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Bingham NS, Zhang X, Ramberger J, Heinonen O, Leighton C, Schiffer P. Collective Ferromagnetism of Artificial Square Spin Ice. Phys Rev Lett 2022; 129:067201. [PMID: 36018663 DOI: 10.1103/physrevlett.129.067201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Revised: 05/04/2022] [Accepted: 06/23/2022] [Indexed: 06/15/2023]
Abstract
We study the temperature and magnetic field dependence of the total magnetic moment of large-area permalloy artificial square spin ice arrays. The temperature dependence and hysteresis behavior are consistent with the coherent magnetization reversal expected in the Stoner-Wohlfarth model, with clear deviations due to interisland interactions at small lattice spacing. Through micromagnetic simulations, we explore this behavior and demonstrate that the deviations result from increasingly complex magnetization reversal at small lattice spacing, induced by interisland interactions, and depending critically on details of the island shapes. These results establish new means to tune the physical properties of artificial spin ice structures and other interacting nanomagnet systems, such as patterned magnetic media.
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Affiliation(s)
- N S Bingham
- Department of Applied Physics, Yale University, New Haven, Connecticut 06511, USA
| | - X Zhang
- Department of Applied Physics, Yale University, New Haven, Connecticut 06511, USA
| | - J Ramberger
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - O Heinonen
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - C Leighton
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - P Schiffer
- Department of Applied Physics, Yale University, New Haven, Connecticut 06511, USA
- Department of Physics, Yale University, New Haven, Connecticut 06511, USA
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2
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Watts JD, Batley JT, Rabideau NA, Hoch JP, O'Brien L, Crowell PA, Leighton C. Finite-Size Effect in Phonon-Induced Elliott-Yafet Spin Relaxation in Al. Phys Rev Lett 2022; 128:207201. [PMID: 35657897 DOI: 10.1103/physrevlett.128.207201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2021] [Accepted: 03/31/2022] [Indexed: 06/15/2023]
Abstract
The Elliott-Yafet theory of spin relaxation in nonmagnetic metals predicts proportionality between spin and momentum relaxation times for scattering centers such as phonons. Here, we test this theory in Al nanowires over a very large thickness range (8.5-300 nm), finding that the Elliott-Yafet proportionality "constant" for phonon scattering in fact exhibits a large, unanticipated finite-size effect. Supported by analytical and numerical modeling, we explain this via strong phonon-induced spin relaxation at surfaces and interfaces, driven in particular by enhanced spin-orbit coupling.
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Affiliation(s)
- J D Watts
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - J T Batley
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - N A Rabideau
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - J P Hoch
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - L O'Brien
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
- Department of Physics, University of Liverpool, Liverpool L69 3BX, United Kingdom
| | - P A Crowell
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - C Leighton
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
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3
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Hameed S, Pelc D, Anderson ZW, Klein A, Spieker RJ, Yue L, Das B, Ramberger J, Lukas M, Liu Y, Krogstad MJ, Osborn R, Li Y, Leighton C, Fernandes RM, Greven M. Enhanced superconductivity and ferroelectric quantum criticality in plastically deformed strontium titanate. Nat Mater 2022; 21:54-61. [PMID: 34608284 DOI: 10.1038/s41563-021-01102-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2020] [Accepted: 08/11/2021] [Indexed: 06/13/2023]
Abstract
The properties of quantum materials are commonly tuned using experimental variables such as pressure, magnetic field and doping. Here we explore a different approach using irreversible, plastic deformation of single crystals. We show that compressive plastic deformation induces low-dimensional superconductivity well above the superconducting transition temperature (Tc) of undeformed SrTiO3, with evidence of possible superconducting correlations at temperatures two orders of magnitude above the bulk Tc. The enhanced superconductivity is correlated with the appearance of self-organized dislocation structures, as revealed by diffuse neutron and X-ray scattering. We also observe deformation-induced signatures of quantum-critical ferroelectric fluctuations and inhomogeneous ferroelectric order using Raman scattering. Our results suggest that strain surrounding the self-organized dislocation structures induces local ferroelectricity and quantum-critical dynamics that strongly influence Tc, consistent with a theory of superconductivity enhanced by soft polar fluctuations. Our results demonstrate the potential of plastic deformation and dislocation engineering for the manipulation of electronic properties of quantum materials.
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Affiliation(s)
- S Hameed
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN, USA
| | - D Pelc
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN, USA.
- Department of Physics, Faculty of Science, University of Zagreb, Zagreb, Croatia.
| | - Z W Anderson
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN, USA
| | - A Klein
- Department of Physics, Faculty of Natural Sciences, Ariel University, Ariel, Israel
| | - R J Spieker
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN, USA
| | - L Yue
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, China
| | - B Das
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN, USA
| | - J Ramberger
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN, USA
| | - M Lukas
- Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, Zagreb, Croatia
| | - Y Liu
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - M J Krogstad
- Materials Science Division, Argonne National Laboratory, Lemont, IL, USA
| | - R Osborn
- Materials Science Division, Argonne National Laboratory, Lemont, IL, USA
| | - Y Li
- International Center for Quantum Materials, School of Physics, Peking University, Beijing, China
| | - C Leighton
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN, USA
| | - R M Fernandes
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN, USA
| | - M Greven
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN, USA.
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4
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Bingham NS, Rooke S, Park J, Simon A, Zhu W, Zhang X, Batley J, Watts JD, Leighton C, Dahmen KA, Schiffer P. Experimental Realization of the 1D Random Field Ising Model. Phys Rev Lett 2021; 127:207203. [PMID: 34860045 DOI: 10.1103/physrevlett.127.207203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 10/06/2021] [Indexed: 06/13/2023]
Abstract
We have measured magnetic-field-induced avalanches in a square artificial spin ice array of interacting nanomagnets. Starting from the ground state ordered configuration, we imaged the individual nanomagnet moments after each successive application of an incrementally increasing field. The statistics of the evolution of the moment configuration show good agreement with the canonical one-dimensional random field Ising model. We extract information about the microscopic structure of the arrays from our macroscopic measurements of their collective behavior, demonstrating a process that could be applied to other systems exhibiting avalanches.
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Affiliation(s)
- N S Bingham
- Department of Applied Physics, Yale University, New Haven, Connecticut 06511, USA
| | - S Rooke
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - J Park
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - A Simon
- Department of Applied Physics, Yale University, New Haven, Connecticut 06511, USA
| | - W Zhu
- Department of Applied Physics, Yale University, New Haven, Connecticut 06511, USA
| | - X Zhang
- Department of Applied Physics, Yale University, New Haven, Connecticut 06511, USA
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - J Batley
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - J D Watts
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - C Leighton
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - K A Dahmen
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - P Schiffer
- Department of Applied Physics, Yale University, New Haven, Connecticut 06511, USA
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Department of Physics, Yale University, New Haven, Connecticut 06511, USA
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5
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Rossi JL, Jiménez JP, Barros P, Assar R, Jaramillo K, Herrera L, Quevedo Y, Botto A, Leighton C, Martínez F. [Depressive symptomatology and psychological well-being among Chilean university students]. Rev Med Chil 2020; 147:579-588. [PMID: 31859890 DOI: 10.4067/s0034-98872019000500579] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Accepted: 04/30/2019] [Indexed: 11/17/2022]
Abstract
BACKGROUND Quality of life and psychological well-being are readily hampered by depression. The changes that students face during college life impact their psychological health and well-being, including the emergence of mental health problems like depression Aim: To determine the relationship between depressive symptoms, sociodemographic parameters and psychological well-being in undergraduate university students. MATERIAL AND METHODS Five hundred eighty university students of both sexes, from the Metropolitan and IX Regions of Chile answered the Beck Depression Inventory (BDI-IA) and the Ryff's psychological well-being scale. RESULTS Twenty eight percent of respondents had clinically significant depressive symptoms, and these were more frequent in women. There was an inverse and statistically significant relationship between psychological well-being and depressive symptoms. This fact was especially marked in dimensions of autonomy, positive relationships with others and purpose in life. CONCLUSIONS There is a high frequency of depressive symptoms among these students. We discuss whether psychological well-being and depressive symptomatology represent two extremes within a continuum or they are two independent dimensions that can account for differential causal mechanisms linked to mental health and illness.
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Affiliation(s)
- José Luis Rossi
- Departamento de Psiquiatría Norte, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Juan Pablo Jiménez
- Departmento de Psiquiatría Oriente, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Paulina Barros
- Departmento de Psiquiatría Oriente, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Rodrigo Assar
- Centro de Medicina Informática y Telemedicina (CIMT), Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | | | - Luisa Herrera
- Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Yamil Quevedo
- Departmento de Psiquiatría Oriente, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Alberto Botto
- Departmento de Psiquiatría Oriente, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Caroline Leighton
- Departmento de Psiquiatría Oriente, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Felipe Martínez
- Facultad de Ciencias Sociales, Pontificia Universidad Católica de Chile, Santiago, Chile
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Leighton C. HOME AND COMMUNITY-BASED PROVIDER PREPARATION FOR PENNSYLVANIA MANAGED LONG-TERM SERVICES AND SUPPORTS. Innov Aging 2018. [DOI: 10.1093/geroni/igy023.2237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- C Leighton
- University of Pittsburgh, Department of Health Policy and Management, Pittsburgh, Pennsylvania, United States
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7
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Jiménez JP, Botto A, Herrera L, Leighton C, Rossi JL, Quevedo Y, Silva JR, Martínez F, Assar R, Salazar LA, Ortiz M, Ríos U, Barros P, Jaramillo K, Luyten P. Psychotherapy and Genetic Neuroscience: An Emerging Dialog. Front Genet 2018; 9:257. [PMID: 30065751 PMCID: PMC6056612 DOI: 10.3389/fgene.2018.00257] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Accepted: 06/26/2018] [Indexed: 12/21/2022] Open
Abstract
Recent research in psychiatric genetics has led to a move away from simple diathesis-stress models to more complex models of psychopathology incorporating a focus on gene–environment interactions and epigenetics. Our increased understanding of the way biology encodes the impact of life events on organisms has also generated more sophisticated theoretical models concerning the molecular processes at the interface between “nature” and “nurture.” There is also increasing consensus that psychotherapy entails a specific type of learning in the context of an emotional relationship (i.e., the therapeutic relationship) that may also lead to epigenetic modifications across different therapeutic treatment modalities. This paper provides a systematic review of this emerging body of research. It is concluded that, although the evidence is still limited at this stage, extant research does indeed suggest that psychotherapy may be associated with epigenetic changes. Furthermore, it is argued that epigenetic studies may play a key role in the identification of biomarkers implicated in vulnerability for psychopathology, and thus may improve diagnosis and open up future research opportunities regarding the mechanism of action of psychotropic drugs as well as psychotherapy. We review evidence suggesting there may be important individual differences in susceptibility to environmental input, including psychotherapy. In addition, given that there is increasing evidence for the transgenerational transmission of epigenetic modifications in animals and humans exposed to trauma and adversity, epigenetic changes produced by psychotherapy may also potentially be passed on to the next generation, which opens up new perspective for prevention science. We conclude this paper stressing the limitations of current research and by proposing a set of recommendations for future research in this area.
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Affiliation(s)
- Juan P Jiménez
- Department of Psychiatry and Mental Health - East, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Alberto Botto
- Department of Psychiatry and Mental Health - East, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Luisa Herrera
- Human Genetics Program, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Caroline Leighton
- Department of Psychiatry and Mental Health - East, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - José L Rossi
- Department of Psychology, Faculty of Social Sciences, Universidad de Chile, Santiago, Chile
| | - Yamil Quevedo
- Department of Psychiatry and Mental Health - East, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Jaime R Silva
- Center for Attachment and Emotional Regulation (CARE), Faculty of Psychology, Universidad del Desarrollo, Santiago, Chile
| | - Felipe Martínez
- Center for Intercultural and Indigenous Research, Anthropology Program, Institute of Sociology, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Rodrigo Assar
- ICBM Human Genetics Program, Centre for Medical Informatics and Telemedicine, Faculty of Medicine, University of Chile, Santiago, Chile
| | - Luis A Salazar
- Center of Molecular Biology and Pharmacogenetics, Department of Basic Sciences, Faculty of Medicine, Universidad de La Frontera, Temuco, Chile
| | - Manuel Ortiz
- Department of Psychology, Faculty of Education, Social Sciences and Humanities, Universidad de La Frontera, Temuco, Chile
| | - Ulises Ríos
- Department of Psychiatry, Universidad de Valparaíso, Valparaíso, Chile
| | - Paulina Barros
- Department of Psychiatry and Mental Health - East, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Karina Jaramillo
- Ph.D. Program in Public Health, School of Public Health, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Patrick Luyten
- Faculty of Psychology and Educational Sciences, KU Leuven, Leuven, Belgium.,Research Department of Clinical, Educational and Health Psychology, University College London, London, United Kingdom
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8
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Rodríguez E, Ruiz JC, Valdés C, Reinel M, Díaz M, Flores J, Crempien C, Leighton C, Botto A, Martínez C, Tomicic A. Estilos de personalidad dependiente y autocrítico: desempeño cognitivo y sintomatología depresiva. Revista Latinoamericana de Psicología 2017. [DOI: 10.1016/j.rlp.2016.09.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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9
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Orth PP, Fernandes RM, Walter J, Leighton C, Shklovskii BI. Percolation via Combined Electrostatic and Chemical Doping in Complex Oxide Films. Phys Rev Lett 2017; 118:106801. [PMID: 28339226 DOI: 10.1103/physrevlett.118.106801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Indexed: 06/06/2023]
Abstract
Stimulated by experimental advances in electrolyte gating methods, we investigate theoretically percolation in thin films of inhomogeneous complex oxides, such as La_{1-x}Sr_{x}CoO_{3} (LSCO), induced by a combination of bulk chemical and surface electrostatic doping. Using numerical and analytical methods, we identify two mechanisms that describe how bulk dopants reduce the amount of electrostatic surface charge required to reach percolation: (i) bulk-assisted surface percolation and (ii) surface-assisted bulk percolation. We show that the critical surface charge strongly depends on the film thickness when the film is close to the chemical percolation threshold. In particular, thin films can be driven across the percolation transition by modest surface charge densities. If percolation is associated with the onset of ferromagnetism, as in LSCO, we further demonstrate that the presence of critical magnetic clusters extending from the film surface into the bulk results in considerable enhancement of the saturation magnetization, with pronounced experimental consequences. These results should significantly guide experimental work seeking to verify gate-induced percolation transitions in such materials.
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Affiliation(s)
- Peter P Orth
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Rafael M Fernandes
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Jeff Walter
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - C Leighton
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - B I Shklovskii
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
- Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455, USA
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10
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Kim KW, O'Brien L, Crowell PA, Leighton C, Stiles MD. Theory of Kondo suppression of spin polarization in nonlocal spin valves. Phys Rev B 2017; 95:104404. [PMID: 28758157 PMCID: PMC5531311 DOI: 10.1103/physrevb.95.104404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We theoretically analyze contributions from the Kondo effect to the spin polarization and spin diffusion length in all-metal nonlocal spin valves. Interdiffusion of ferromagnetic atoms into the normal metal layer creates a region in which Kondo physics plays a significant role, giving discrepancies between experiment and existing theory. We start from a simple model and construct a modified spin drift-diffusion equation which clearly demonstrates how the Kondo physics not only suppresses the electrical conductivity but even more strongly reduces the spin diffusion length. We also present an explicit expression for the suppression of spin polarization due to Kondo physics in an illustrative regime. We compare this theory to previous experimental data to extract an estimate of the Elliot-Yafet probability for Kondo spin flip scattering of 0.7 ± 0.4, in good agreement with the value of 2/3 derived in the original theory of Kondo.
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Affiliation(s)
- K-W Kim
- Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
- Maryland NanoCenter, University of Maryland, College Park, Maryland 20742, USA
- Institut für Physik, Johannes Gutenberg Universitat Mainz, Mainz 55128, Germany
| | - L O'Brien
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minnesota 55455, USA
- Thin Film Magnetism, Cavendish Laboratory, University of Cambridge, CB3 0HE, UK
- Department of Physics, University of Liverpool, Liverpool L69 7ZE, UK
| | - P A Crowell
- School of Physics and Astronomy, University of Minnesota, Minnesota 55455, USA
| | - C Leighton
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minnesota 55455, USA
| | - M D Stiles
- Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
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11
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Leighton C, Botto A, Silva JR, Jiménez JP, Luyten P. Vulnerability or Sensitivity to the Environment? Methodological Issues, Trends, and Recommendations in Gene-Environment Interactions Research in Human Behavior. Front Psychiatry 2017; 8:106. [PMID: 28674505 PMCID: PMC5475387 DOI: 10.3389/fpsyt.2017.00106] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Accepted: 05/31/2017] [Indexed: 12/29/2022] Open
Abstract
Research on the potential role of gene-environment interactions (GxE) in explaining vulnerability to psychopathology in humans has witnessed a shift from a diathesis-stress perspective to differential susceptibility approaches. This paper critically reviews methodological issues and trends in this body of research. Databases were screened for studies of GxE in the prediction of personality traits, behavior, and mental health disorders in humans published between January 2002 and January 2015. In total, 315 papers were included. Results showed that 34 candidate genes have been included in GxE studies. Independent of the type of environment studied (early or recent life events, positive or negative environments), about 67-83% of studies have reported significant GxE interactions, which is consistent with a social susceptibility model. The percentage of positive results does not seem to differ depending on the gene studied, although publication bias might be involved. However, the number of positive findings differs depending on the population studied (i.e., young adults vs. older adults). Methodological considerations limit the ability to draw strong conclusions, particularly as almost 90% (n = 283/315) of published papers are based on samples from North America and Europe, and about 70% of published studies (219/315) are based on samples that were also used in other reports. At the same time, there are clear indications of methodological improvements over time, as is shown by a significant increase in longitudinal and experimental studies as well as in improved minimum genotyping. Recommendations for future research, such as minimum quality assessment of genes and environmental factors, specifying theoretical models guiding the study, and taking into account of cultural, ethnic, and lifetime perspectives, are formulated.
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Affiliation(s)
- Caroline Leighton
- Departamento de Psiquiatria y Salud Mental Oriente, Universidad de Chile, Santiago, Chile.,Millennium Institute for Research in Depression and Personality - MIDAP, Ministry of Economy, Santiago, Chile
| | - Alberto Botto
- Departamento de Psiquiatria y Salud Mental Oriente, Universidad de Chile, Santiago, Chile.,Millennium Institute for Research in Depression and Personality - MIDAP, Ministry of Economy, Santiago, Chile
| | - Jaime R Silva
- Millennium Institute for Research in Depression and Personality - MIDAP, Ministry of Economy, Santiago, Chile.,Centro de Apego y Regulación Emocional (CARE), Facultad de Psicología, Universidad del Desarrollo, Santiago, Chile.,Clinica Alemana de Santiago, Santiago, Chile
| | - Juan Pablo Jiménez
- Departamento de Psiquiatria y Salud Mental Oriente, Universidad de Chile, Santiago, Chile.,Millennium Institute for Research in Depression and Personality - MIDAP, Ministry of Economy, Santiago, Chile
| | - Patrick Luyten
- Millennium Institute for Research in Depression and Personality - MIDAP, Ministry of Economy, Santiago, Chile.,Clinical Psychology, University of Leuven, Leuven, Belgium.,Research Department of Clinical, Educational and Health Psychology, University College London, London, United Kingdom
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12
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Xie W, Wang S, Zhang X, Leighton C, Frisbie CD. High conductance 2D transport around the Hall mobility peak in electrolyte-gated rubrene crystals. Phys Rev Lett 2014; 113:246602. [PMID: 25541790 DOI: 10.1103/physrevlett.113.246602] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Indexed: 06/04/2023]
Abstract
We report the observation of the Hall effect at hole densities up to 6×10¹³ cm⁻² (0.3 holes/molecule) on the surface of electrolyte-gated rubrene crystals. The perplexing peak in the conductance as a function of gate voltage is confirmed to result from a maximum in mobility, which reaches 4 cm² V⁻¹ s⁻¹ at 2.5×10¹³ cm⁻². Measurements to liquid helium temperatures reveal that this peak is markedly asymmetric, with bandlike and hopping-type transport occurring on the low density side, while unconventional, likely electrostatic-disorder-affected transport dominates the high density side. Most significantly, near the mobility peak the temperature coefficient of the resistance remains positive to as low as 120 K, the low temperature resistance becomes weakly temperature dependent, and the conductance reaches within a factor of 2 of e²/h, revealing conduction unprecedentedly close to a two-dimensional metallic state.
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Affiliation(s)
- Wei Xie
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Shun Wang
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Xin Zhang
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - C Leighton
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - C Daniel Frisbie
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
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13
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Baruth A, Seo M, Lin CH, Walster K, Shankar A, Hillmyer MA, Leighton C. Optimization of long-range order in solvent vapor annealed poly(styrene)-block-poly(lactide) thin films for nanolithography. ACS Appl Mater Interfaces 2014; 6:13770-81. [PMID: 25029410 DOI: 10.1021/am503199d] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Detailed experiments designed to optimize and understand the solvent vapor annealing of cylinder-forming poly(styrene)-block-poly(lactide) thin films for nanolithographic applications are reported. By combining climate-controlled solvent vapor annealing (including in situ probes of solvent concentration) with comparative small-angle X-ray scattering studies of solvent-swollen bulk polymers of identical composition, it is concluded that a narrow window of optimal solvent concentration occurs just on the ordered side of the order-disorder transition. In this window, the lateral correlation length of the hexagonally close-packed ordering, the defect density, and the cylinder orientation are simultaneously optimized, resulting in single-crystal-like ordering over 10 μm scales. The influences of polymer synthesis method, composition, molar mass, solvent vapor pressure, evaporation rate, and film thickness have all been assessed, confirming the generality of this behavior. Analogies to thermal annealing of elemental solids, in combination with an understanding of the effects of process parameters on annealing conditions, enable qualitative understanding of many of the key results and underscore the likely generality of the main conclusions. Pattern transfer via a Damascene-type approach verified the applicability for high-fidelity nanolithography, yielding large-area metal nanodot arrays with center-to-center spacing of 38 nm (diameter 19 nm). Finally, the predictive power of our findings was demonstrated by using small-angle X-ray scattering to predict optimal solvent annealing conditions for poly(styrene)-block-poly(lactide) films of low molar mass (18 kg mol(-1)). High-quality templates with cylinder center-to-center spacing of only 18 nm (diameter of 10 nm) were obtained. These comprehensive results have clear and important implications for optimization of pattern transfer templates and significantly advance the understanding of self-assembly in block copolymer thin films.
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Affiliation(s)
- A Baruth
- Department of Chemical Engineering and Materials Science and Department of Chemistry, University of Minnesota , Minneapolis, Minnesota 55455-0431, United States
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14
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Caballero-Flores R, Bingham NS, Phan MH, Torija MA, Leighton C, Franco V, Conde A, Phan TL, Yu SC, Srikanth H. Magnetocaloric effect and critical behavior in Pr0.5Sr0.5MnO3: an analysis of the validity of the Maxwell relation and the nature of the phase transitions. J Phys Condens Matter 2014; 26:286001. [PMID: 24945593 DOI: 10.1088/0953-8984/26/28/286001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The Maxwell relation, the Clausius-Clapeyron equation, and a non-iterative method to obtain the critical exponents have been used to characterize the magnetocaloric effect (MCE) and the nature of the phase transitions in Pr0.5Sr0.5MnO3, which undergoes a second-order paramagnetic to ferromagnetic (PM-FM) transition at TC ~ 247 K, and a first-order ferromagnetic to antiferromagnetic (FM-AFM) transition at TN ~ 165 K. We find that around the second-order PM-FM transition, the MCE (as represented by the magnetic entropy change, ΔSM) can be precisely determined from magnetization measurements using the Maxwell relation. However, around the first-order FM-AFM transition, values of ΔSM calculated with the Maxwell relation deviate significantly from those calculated by the Clausius-Clapeyron equation at the magnetic field and temperature ranges where a conversion between the AFM and FM phases occurs. A detailed analysis of the critical exponents of the second-order PM-FM transition allows us to correlate the short-range type magnetic interactions with the MCE. Using the Arrott-Noakes equation of state with the appropriate values of the critical exponents, the field- and temperature-dependent magnetization [Formula: see text] curves, and hence the [Formula: see text] curves, have been simulated and compared with experimental data. A good agreement between the experimental and simulated data has been found in the vicinity of the Curie temperature TC, but a noticeable discrepancy is present for [Formula: see text]. This discrepancy arises mainly from the coexistence of AFM and FM phases and the presence of ferromagnetic clusters in the AFM matrix.
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Affiliation(s)
- R Caballero-Flores
- Department of Physics, University of South Florida, Tampa, FL 33620, USA. Departamento de Física de la Materia Condensada, ICMSE-CSIC, Universidad de Sevilla, 41080 Sevilla, Spain. Departamento de Física, Universidad de Oviedo, 33007 Oviedo, Spain
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15
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O'Brien L, Erickson MJ, Spivak D, Ambaye H, Goyette RJ, Lauter V, Crowell PA, Leighton C. Kondo physics in non-local metallic spin transport devices. Nat Commun 2014; 5:3927. [PMID: 24873934 DOI: 10.1038/ncomms4927] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Accepted: 04/22/2014] [Indexed: 11/09/2022] Open
Abstract
The non-local spin-valve is pivotal in spintronics, enabling separation of charge and spin currents, disruptive potential applications and the study of pressing problems in the physics of spin injection and relaxation. Primary among these problems is the perplexing non-monotonicity in the temperature-dependent spin accumulation in non-local ferromagnetic/non-magnetic metal structures, where the spin signal decreases at low temperatures. Here we show that this effect is strongly correlated with the ability of the ferromagnetic to form dilute local magnetic moments in the NM. This we achieve by studying a significantly expanded range of ferromagnetic/non-magnetic combinations. We argue that local moments, formed by ferromagnetic/non-magnetic interdiffusion, suppress the injected spin polarization and diffusion length via a manifestation of the Kondo effect, thus explaining all observations. We further show that this suppression can be completely quenched, even at interfaces that are highly susceptible to the effect, by insertion of a thin non-moment-supporting interlayer.
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Affiliation(s)
- L O'Brien
- 1] Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA [2] Thin Film Magnetism, Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK
| | - M J Erickson
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - D Spivak
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - H Ambaye
- Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - R J Goyette
- Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - V Lauter
- Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - P A Crowell
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - C Leighton
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
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16
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Rice WD, Ambwani P, Bombeck M, Thompson JD, Haugstad G, Leighton C, Crooker SA. Persistent optically induced magnetism in oxygen-deficient strontium titanate. Nat Mater 2014; 13:481-487. [PMID: 24658116 DOI: 10.1038/nmat3914] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2013] [Accepted: 02/12/2014] [Indexed: 06/03/2023]
Abstract
Strontium titanate (SrTiO3) is a foundational material in the emerging field of complex oxide electronics. Although its bulk electronic and optical properties are rich and have been studied for decades, SrTiO3 has recently become a renewed focus of materials research catalysed in part by the discovery of superconductivity and magnetism at interfaces between SrTiO3 and other non-magnetic oxides. Here we illustrate a new aspect to the phenomenology of magnetism in SrTiO3 by reporting the observation of an optically induced and persistent magnetization in slightly oxygen-deficient bulk SrTiO3-δ crystals using magnetic circular dichroism (MCD) spectroscopy and SQUID magnetometry. This zero-field magnetization appears below ~18 K, persists for hours below 10 K, and is tunable by means of the polarization and wavelength of sub-bandgap (400-500 nm) light. These effects occur only in crystals containing oxygen vacancies, revealing a detailed interplay between magnetism, lattice defects, and light in an archetypal complex oxide material.
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Affiliation(s)
- W D Rice
- National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - P Ambwani
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - M Bombeck
- Experimentelle Physik 2, Technische Universität Dortmund, D-44227 Dortmund, Germany
| | - J D Thompson
- Materials Physics and Applications, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - G Haugstad
- Characterization Facility, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - C Leighton
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - S A Crooker
- National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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17
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Abstract
Oxcarbazepine is an antiepileptic drug that has been approved by the US FDA and is indicated for use as monotherapy or adjunctive therapy in the treatment of partial seizures in adults and children aged over 4 years. The aim of this report is to investigate the results of clinical trials in order to ascertain the efficacy and safety of oxcarbazepine for use in bipolar disorder and schizoaffective disorder. Oxcarbazepine is a keto-congener of carbamazepine with fewer side effects and drug interactions. Orally administrated oxcarbazepine is rapidly and completely absorbed and has a half-life of 9 h. Currently, there is a lack of controlled clinical trials studying the use of oxcarbazepine. In light of controlled and open-label prospective studies, it may be useful for manic symptoms in the treatment of bipolar and schizoaffective patients. Case reports, retrospective and prospective studies suggest that oxcarbazepine might have prophylactic efficacy and long-term benefit for these patients. In addition, owing to its lower propensity for drug interactions and side effects, it may be useful in the treatment of refractory patients with bipolar and schizoaffective disorder. However, most of the trials have relevant methodological shortcomings. The side-effect profile of oxcarbazepine is similar to carbamazepine, but the severity of these effects appears to be slightly less. The symptoms that are most frequently associated with the use of oxcarbazepine are asthenia, headache, dizziness, somnolence, nausea, diplopia and skin rash. Isolated cases of hyponatremic coma have been reported, thus electrolyte abnormalities should be closely monitored. Oxcarbazepine is now a generic drug, but the metabolite licarbazepine and other related compounds, such as eslicarbazepine, are currently being studied under controlled conditions and might become useful therapies for bipolar and schizoaffective disorder in the future.
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Affiliation(s)
- Ekaterine Popova
- Clinical Institute of Neuroscience, Hospital Clìnic, University of Barcelona, IDIBAPS, Barcelona, Spain.
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18
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Zhang X, Wu N, Manno M, Leighton C, Vescovo E, Dowben PA. Resonant photoemission and spin polarization of Co(1-x)Fe(x)S(2). J Phys Condens Matter 2013; 25:012001. [PMID: 23160359 DOI: 10.1088/0953-8984/25/1/012001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The valence band occupied state electronic structure of Co(1-x)Fe(x)S(2) in the region of the Fe/Co 3d bands has been investigated using photoemission and spin-polarized photoemission. As measured by using spin-polarized ultraviolet photoemission, the surface Fermi level spin polarization of Co(1-x)Fe(x)S(2) thin films at 50 K, specifically at x = 0, 0.05, 0.10 and 0.15, was found to be much reduced compared to that of the bulk. The spin polarization nonetheless increases with Fe concentration. The resonant photoemission spectroscopy provides evidence that S bands have a strong resonance at the photon energy corresponding to the Co 2p core level, indicating strong hybridization between Co and S bands in Co(1-x)Fe(x)S(2) (at small x). Similar evidence exists for Fe hybridization with the S bands.
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Affiliation(s)
- Xin Zhang
- Nebraska Center for Materials and Nanoscience, Department of Physics and Astronomy, University of Nebraska-Lincoln, 68588-0299, USA
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19
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Wang S, Ha M, Manno M, Daniel Frisbie C, Leighton C. Hopping transport and the Hall effect near the insulator–metal transition in electrochemically gated poly(3-hexylthiophene) transistors. Nat Commun 2012; 3:1210. [DOI: 10.1038/ncomms2213] [Citation(s) in RCA: 138] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Accepted: 10/19/2012] [Indexed: 11/09/2022] Open
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20
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Chen TY, Erickson MJ, Crowell PA, Leighton C. Surface roughness dominated pinning mechanism of magnetic vortices in soft ferromagnetic films. Phys Rev Lett 2012; 109:097202. [PMID: 23002875 DOI: 10.1103/physrevlett.109.097202] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Indexed: 06/01/2023]
Abstract
Although pinning of domain walls in ferromagnets is ubiquitous, the absence of an appropriate characterization tool has limited the ability to correlate the physical and magnetic microstructures of ferromagnetic films with specific pinning mechanisms. Here, we show that the pinning of a magnetic vortex, the simplest possible domain structure in soft ferromagnets, is strongly correlated with surface roughness, and we make a quantitative comparison of the pinning energy and spatial range in films of various thickness. The results demonstrate that thickness fluctuations on the lateral length scale of the vortex core diameter, i.e., an effective roughness at a specific length scale, provides the dominant pinning mechanism. We argue that this mechanism will be important in virtually any soft ferromagnetic film.
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Affiliation(s)
- T Y Chen
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
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21
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Zhang S, Li J, Gilbert I, Bartell J, Erickson MJ, Pan Y, Lammert PE, Nisoli C, Kohli KK, Misra R, Crespi VH, Samarth N, Leighton C, Schiffer P. Perpendicular magnetization and generic realization of the Ising model in artificial spin ice. Phys Rev Lett 2012; 109:087201. [PMID: 23002770 DOI: 10.1103/physrevlett.109.087201] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Indexed: 06/01/2023]
Abstract
We have studied frustrated kagome arrays and unfrustrated honeycomb arrays of magnetostatically interacting single-domain ferromagnetic islands with magnetization normal to the plane. The measured pairwise spin correlations of both lattices can be reproduced by models based solely on nearest-neighbor correlations. The kagome array has qualitatively different magnetostatics but identical lattice topology to previously studied artificial spin ice systems composed of in-plane moments. The two systems show striking similarities in the development of moment pair correlations, demonstrating a universality in artificial spin ice behavior independent of specific realization in a particular material system.
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Affiliation(s)
- Sheng Zhang
- Department of Physics and Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA
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22
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Rodwogin MD, Baruth A, Jackson EA, Leighton C, Hillmyer MA. Nanoscale rings from silicon-containing triblock terpolymers. ACS Appl Mater Interfaces 2012; 4:3550-3557. [PMID: 22757616 DOI: 10.1021/am300603x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Nanoscopic ring arrays of various materials show promise for both technological applications and fundamental studies. In this work we report the preparation of sub-50 nm diameter ring arrays from metallic thin films using a block polymer lithographic pattern transfer approach. We prepared a triblock terpolymer that adopts a core-shell cylindrical morphology where the shell is an oxidizable polydimethylsiloxane block. Solvent annealed thin films of this terpolymer produce cylindrical features oriented perpendicular to the substrate surface. The polydimethylsiloxane shell is then converted into SiOx rings by an oxygen reactive ion etch. The resultant hard mask pattern is then transferred into Au, Ni80Fe20, and Ni80Cr20 thin films via Ar ion beam milling, demonstrating the generality of the approach.
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Affiliation(s)
- Marc D Rodwogin
- Department of Chemistry and §Department of Chemical Engineering and Material Science, University of Minnesota , Minneapolis, Minnesota 55455, United States
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Kim SW, Kim SH, Halasyamani PS, Green MA, Bhatti KP, Leighton C, Das H, Fennie CJ. RbFe2+Fe3+F6: Synthesis, structure, and characterization of a new charge-ordered magnetically frustrated pyrochlore-related mixed-metal fluoride. Chem Sci 2012. [DOI: 10.1039/c2sc00765g] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Baruth A, Rodwogin MD, Shankar A, Erickson MJ, Hillmyer MA, Leighton C. Non-lift-off block copolymer lithography of 25 nm magnetic nanodot arrays. ACS Appl Mater Interfaces 2011; 3:3472-3481. [PMID: 21830808 DOI: 10.1021/am200693x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Although nanolithographic techniques based on self-assembled block copolymer templates offer tremendous potential for fabrication of large-area nanostructure arrays, significant difficulties arise with both the lift-off and etch processes typically used for pattern transfer. These become progressively more important in the limit of extreme feature sizes. The few techniques that have been developed to avoid these issues are quite complex. Here, we demonstrate successful execution of a nanolithographic process based on solvent annealed, cylinder-forming, easily degradable, polystyrene-b-polylactide block copolymer films that completely avoids lift-off in addition to the most challenging aspects of etching. We report a "Damascene-type" process that overfills the polystyrene template with magnetic metal, employs ion beam milling to planarize the metal surface down to the underlying polystyrene template, then exploits the large etch rate contrast between polystyrene and typical metals to generate pattern reversal of the original template into the magnetic metal. The process is demonstrated via formation of a large-area array of 25 nm diameter ferromagnetic Ni(80)Fe(20) nanodots with hexagonally close-packed order. Extensive microscopy, magnetometry, and electrical measurements provide detailed characterization of the pattern formation. We argue that the approach is generalizable to a wide variety of materials, is scalable to smaller feature sizes, and critically, minimizes etch damage, thus preserving the essential functionality of the patterned material.
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Affiliation(s)
- A Baruth
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, United States
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25
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Barrientos C, Xaus G, Leighton C, Martin J, Gordan VV, Moncada G. Oxalic Acid Under Adhesive Restorations as a Means to Reduce Dentin Sensitivity: A Four-Month Clinical Trial. Oper Dent 2011; 36:126-32. [DOI: 10.2341/09-364-c] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Clinical Relevance
Oxalic acid may offer a novel approach to improve the reduction of dentin postoperative sensitivity after placement of resin-bonded restorations.
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26
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Nuevo R, Leighton C, Dunn G, Dowrick C, Lehtinen V, Dalgard OS, Casey P, Vázquez-Barquero JL, Ayuso-Mateos JL. Impact of severity and type of depression on quality of life in cases identified in the community. Psychol Med 2010; 40:2069-2077. [PMID: 20146833 DOI: 10.1017/s0033291710000164] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND The impact of different levels of depression severity on quality of life (QoL) is not well studied, particularly regarding ICD-10 criteria. The ICD classification of depressive episodes in three levels of severity is also controversial and the less severe category, mild, has been considered as unnecessary and not clearly distinguishable from non-clinical states. The present work aimed to test the relationship between depression severity according to ICD-10 criteria and several dimensions of functioning as assessed by Medical Outcome Study (MOS) 36-item Short Form general health survey (SF-36) at the population level. METHOD A sample of 551 participants from the second phase of the Outcome of Depression International Network (ODIN) study (228 controls without depression and 313 persons fulfilling ICD criteria for depressive episode) was selected for a further assessment of several variables, including QoL related to physical and mental health as measured with the SF-36. RESULTS Statistically significant differences between controls and the depression group were found in both physical and mental markers of health, regardless of the level of depression severity; however, there were very few differences in QoL between levels of depression as defined by ICD-10. Regardless of the presence of depression, disability, widowed status, being a woman and older age were associated with worse QoL in a structural equation analysis with covariates. Likewise, there were no differences according to the type of depression (single-episode versus recurrent). CONCLUSIONS These results cast doubt on the adequacy of the current ICD classification of depression in three levels of severity.
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Affiliation(s)
- R Nuevo
- Department of Psychiatry, Hospital Universitario de la Princesa, Universidad Autónoma de Madrid, Madrid, Spain
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27
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Rodwogin MD, Spanjers CS, Leighton C, Hillmyer MA. Polylactide-poly(dimethylsiloxane)-polylactide triblock copolymers as multifunctional materials for nanolithographic applications. ACS Nano 2010; 4:725-732. [PMID: 20112923 DOI: 10.1021/nn901190a] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Highly immiscible block copolymers are attractive materials for applications in nanolithography due to their ability to self-assemble on length scales that are difficult to access by conventional lithography. The incorporation of inorganic domains into such block copolymers provides etch contrast that can potentially reduce processing times and costs in nanolithographic applications. We explored thin films of polylactide-poly(dimethylsiloxane)-polylactide (PLA-PDMS-PLA) triblock copolymers as multifunctional nanolithographic templates. We demonstrate the formation of well-ordered arrays of hexagonally packed PDMS cylinders oriented normal to the substrate, the orthogonal etchability of these cylinders and the PLA matrix, and the formation of etch-resistant domains that can be used as pattern transfer masks.
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Affiliation(s)
- Marc D Rodwogin
- Department of Chemistry, University of Minnesota, Minneapolis, MN 55455-0431, USA
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28
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Leighton C. Be careful about timelines. CMAJ 2010; 182:63. [DOI: 10.1503/cmaj.110-2007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
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29
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Utfeld C, Giblin SR, Taylor JW, Duffy JA, Shenton-Taylor C, Laverock J, Dugdale SB, Manno M, Leighton C, Itou M, Sakurai Y. Bulk spin polarization of Co(1-x)Fe(x)S2. Phys Rev Lett 2009; 103:226403. [PMID: 20366116 DOI: 10.1103/physrevlett.103.226403] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2009] [Indexed: 05/29/2023]
Abstract
We report on a new method to determine the degree of bulk spin polarization in single crystal Co(1-x)Fe(x)S2 by modeling magnetic Compton scattering with ab initio calculations. Spin-dependent Compton profiles were measured for CoS2 and Co0.9Fe0.1S2. The ab initio calculations were then refined by rigidly shifting the bands to provide the best fit between the calculated and experimental directional profiles for each sample. The bulk spin polarizations, P, corresponding to the spin-polarized density of states at the Fermi level, were then extracted from the refined calculations. The values were found to be P=-72+/-6% and P=18+/-7% for CoS2 and Co0.9Fe0.1S2, respectively. Furthermore, determinations of P weighted by the Fermi velocity (v(F) or v(F)2) were obtained, permitting a rigorous comparison with other experimental data and highlighting the experimental dependence of P on v(F).
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Affiliation(s)
- C Utfeld
- H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, United Kingdom
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Leighton C, Hoffmann A, Fitzsimmons MR, Nogués J, Schuller IK. Deposition of epitaxial α-Fe2O3 layers for exchange bias studies by reactive dc magnetron sputtering. ACTA ACUST UNITED AC 2009. [DOI: 10.1080/13642810110061501] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Affiliation(s)
- C. Leighton
- a Physics Department , University of California , San Diego , La Jolla California , 92093-0319 , USA
- d Department of Chemical Engineering and Materials Science , University of Minnesota , Minneapolis 55455 , USA
| | - A. Hoffmann
- b Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , USA
| | - M. R. Fitzsimmons
- a Physics Department , University of California , San Diego , La Jolla California , 92093-0319 , USA
| | - J. Nogués
- c Departament de Física , Universitat Autónoma de Barcelona , 08193 , Bellaterra , Spain
| | - Ivan K. Schuller
- a Physics Department , University of California , San Diego , La Jolla California , 92093-0319 , USA
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31
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Wu N, Sabirianov RF, Mei WN, Losovyj YB, Lozova N, Manno M, Leighton C, Dowben PA. The minority spin surface bands of CoS(2)(001). J Phys Condens Matter 2009; 21:295501. [PMID: 21828532 DOI: 10.1088/0953-8984/21/29/295501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Angle-resolved photoemission was used to study the surface electronic band structure of high quality single crystals of ferromagnetic CoS(2) (below 120 K). Strongly dispersing Co t(2g) bands are identified along the ⟨100⟩ [Formula: see text] direction, the [Formula: see text]-[Formula: see text] line of the surface Brillouin zone, in agreement with model calculations. The calculated surface band structure includes corrections for the previously determined surface structure of CoS(2)(001) and is in general agreement with the experimental photoemission spectra in the region of the Fermi level. There is evidence of the existence of several minority spin surface states, falling into a gap of the projected minority spin bulk CoS(2)(001) band structure.
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Affiliation(s)
- Ning Wu
- Department of Physics and Astronomy and the Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE 68588-0111, USA
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Abstract
Block polymers offer an attractive route to densely packed, monodisperse nanoscale pores. However, their fragility as thin films complicates their use as membranes. By integrating a block polymer film with a thin (100 microm) silicon substrate, we have developed a composite membrane providing both nanoscale size exclusion and fast transport of small molecules. Here we describe the fabrication of this membrane, evaluate its mechanical integrity, and demonstrate its transport properties for model solutes of large and small molecular weight. The ability to block large molecules without hindering smaller ones, coupled with the potential for surface modification of the polymer and the microelectromechanical system style of support, makes this composite membrane an attractive candidate for interfacing implantable sensing and drug-delivery devices with biological hosts.
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Affiliation(s)
- Eric E Nuxoll
- Department of Pharmaceutics, University of Minnesota, Minneapolis, Minnesota 55455, USA
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Leighton C, Manno M, Cady A, Freeland JW, Wang L, Umemoto K, Wentzcovitch RM, Chen TY, Chien CL, Kuhns PL, Hoch MJR, Reyes AP, Moulton WG, Dahlberg ED, Checkelsky J, Eckert J. Composition controlled spin polarization in Co(1-x)Fe(x)S(2) alloys. J Phys Condens Matter 2007; 19:315219. [PMID: 21694119 DOI: 10.1088/0953-8984/19/31/315219] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The transition metal (TM) chalcogenides of the form TMX(2) (X = S or Se) have been studied for decades due to their interesting electronic and magnetic properties such as metamagnetism and metal-insulator transitions. In particular, the Co(1-x)Fe(x)S(2) alloys were the subject of investigation in the 1970s due to general interest in itinerant ferromagnetism. In recent years (2000-present) it has been shown, both by electronic structure calculations and detailed experimental investigations, that Co(1-x)Fe(x)S(2) is a model system for the investigation of highly spin polarized ferromagnetism. The radically different electronic properties of the two endpoint compounds (CoS(2) is a narrow bandwidth ferromagnetic metal, while FeS(2) is a diamagnetic semiconductor), in a system forming a substitutional solid solution allows for composition control of the Fermi level relative to the spin split bands, and therefore composition-controlled conduction electron spin polarization. In essence, the recent work has shown that the concept of 'band engineering' can be applied to half-metallic ferromagnets and that high spin polarization can be deliberately engineered. Experiments reveal tunability in both sign and magnitude of the spin polarization at the Fermi level, with maximum values obtained to date of 85% at low temperatures. In this paper we review the properties of Co(1-x)Fe(x)S(2) alloys, with an emphasis on properties of relevance to half-metallicity. Crystal structure, electronic structure, synthesis, magnetic properties, transport properties, direct probes of the spin polarization, and measurements of the total density of states at the Fermi level are all discussed. We conclude with a discussion of the factors that influence, or even limit, the spin polarization, along with a discussion of opportunities and problems for future investigation, particularly with regard to fundamental studies of spintronic devices.
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Affiliation(s)
- C Leighton
- Department of Chemical Engineering and Materials Science, University of Minnesota, USA
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Klie RF, Zheng JC, Zhu Y, Varela M, Wu J, Leighton C. Direct measurement of the low-temperature spin-state transition in LaCoO3. Phys Rev Lett 2007; 99:047203. [PMID: 17678397 DOI: 10.1103/physrevlett.99.047203] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2006] [Indexed: 05/16/2023]
Abstract
LaCoO3 exhibits an anomaly in its magnetic susceptibility around 80 K associated with a thermally excited transition of the Co3+-ion spin. We show that electron energy-loss spectroscopy is sensitive to this Co3+-ion spin-state transition, and that the O K edge prepeak provides a direct measure of the Co3+ spin state in LaCoO3 as a function of temperature. Our experimental results are confirmed by first-principles calculations, and we conclude that the thermally excited spin-state transition occurs from a low to an intermediate spin state, which can be distinguished from the high-spin state.
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Affiliation(s)
- R F Klie
- Department of Physics, University of Illinois at Chicago, Chicago, Illinois 60657, USA
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35
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Leighton C, Fisher B, Macdonald D, Stitt L, Bauman G, Cairncross J. The dose–volume interaction in adult supratentorial low-grade glioma: higher radiation dose is beneficial among patients with partial resection. J Neurooncol 2007; 82:165-70. [PMID: 17357830 DOI: 10.1007/s11060-006-9141-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2005] [Accepted: 03/01/2006] [Indexed: 10/23/2022]
Abstract
PURPOSE To evaluate the hypothesis that adults with partially resected (PR<50% resection) supratentorial low-grade glioma (LGG) benefit from higher doses of radiation. METHODS Patients receiving post-operative radiation for WHO grade I-II LGG at the University of Western Ontario between 1979 and 2001 were studied. Patient characteristics evaluated included: age, gender, symptom duration>30 days, seizures at presentation, Karnofsky performance status (KPS)<70, astrocytoma pathology (AS), and radiation dose. A Cox proportional hazard regression model was constructed to test the influence of radiation dose. RESULTS One hundred and seven patients were analyzed. Patients who had PR were not significantly different from those with STR (subtotal/total resection) in terms of patient characteristics. Median survival (MST) of PR patients who received<or=50 Gy was 16.5 months while those who received>50 Gy had a MST of 109.2 months. The interaction of radiation dose and extent of resection was tested after controlling for other patient factors by Cox regression model. The interaction was highly significant for both OS and PFS (P=0.013 and P=0.003, respectively). This model remained significant after excluding six patients receiving doses<42 Gy (OS, P=0.024, and PFS, P=0.001). CONCLUSIONS The outcome for patients with LGG is dependent on extent of tumor resection and radiation dose. Patients with PR should be considered for higher radiation dose schedules (>50 Gy). Future trials on therapeutic strategies for LGG should consider stratification of patients by extent of tumor resection. Our data suggests that one dose does not fit all.
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Affiliation(s)
- C Leighton
- Division of Radiation Oncology, London Regional Cancer Centre Program, London Health Sciences Hospital, and Department of Medical Oncology, University of Western Ontario, London, Ontario, Canada.
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36
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Parker JS, Wang L, Steiner KA, Crowell PA, Leighton C. Exchange bias as a probe of the incommensurate spin-density wave in epitaxial Fe/Cr(001). Phys Rev Lett 2006; 97:227206. [PMID: 17155839 DOI: 10.1103/physrevlett.97.227206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2006] [Indexed: 05/12/2023]
Abstract
We report clear multiple period oscillations in the temperature dependence of exchange bias in an Fe thin film exchange coupled to a neighboring Cr film. The oscillations arise due to an incommensurate spin-density wave in the Cr, with wave vector perpendicular to the Fe/Cr(001) interface. The exchange bias and coercivity allow for a determination of the extent of the thermally driven wavelength expansion, the (strain-suppressed) spin-flip transition temperature, and the Cr Néel temperature, which show a crossover from bulklike to finite-size behavior at a Cr thickness of approximately 1100 A. The data are consistent with a transition from a transverse to longitudinal wave on cooling.
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Affiliation(s)
- J S Parker
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
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37
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Kuhns PL, Hoch MJR, Reyes AP, Moulton WG, Wang L, Leighton C. Evolution with composition of the d-band density of states at the Fermi level in highly spin polarized Co1-xFexS2. Phys Rev Lett 2006; 96:167208. [PMID: 16712272 DOI: 10.1103/physrevlett.96.167208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2005] [Revised: 01/30/2006] [Indexed: 05/09/2023]
Abstract
Highly spin polarized (SP) and half-metallic ferromagnetic systems are of considerable current interest and of potential importance for spintronic applications. Recent work has demonstrated that Co1-xFexS2 is a highly polarized ferromagnet (FM) where the spin polarization can be tuned by alloy composition. Using 59Co FM-NMR as a probe, we have measured the low-temperature spin relaxation in this system in magnetic fields from 0 to 1.0 T for 0<or=x<or=0.3. The 59Co spin-lattice relaxation rates follow a linear T dependence. Analysis of the data, using expressions for a FM system, permits information to be obtained on the d-band density of states at the Fermi level. The results are compared with independent density of states values inferred from electronic specific heat measurements and band structure calculations. It is shown that FM-NMR can be an important method for investigating highly SP systems.
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Affiliation(s)
- P L Kuhns
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, USA
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38
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Wang RF, Nisoli C, Freitas RS, Li J, McConville W, Cooley BJ, Lund MS, Samarth N, Leighton C, Crespi VH, Schiffer P. Artificial ‘spin ice’ in a geometrically frustrated lattice of nanoscale ferromagnetic islands. Nature 2006; 439:303-6. [PMID: 16421565 DOI: 10.1038/nature04447] [Citation(s) in RCA: 653] [Impact Index Per Article: 36.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2005] [Accepted: 11/16/2005] [Indexed: 11/08/2022]
Abstract
Frustration, defined as a competition between interactions such that not all of them can be satisfied, is important in systems ranging from neural networks to structural glasses. Geometrical frustration, which arises from the topology of a well-ordered structure rather than from disorder, has recently become a topic of considerable interest. In particular, geometrical frustration among spins in magnetic materials can lead to exotic low-temperature states, including 'spin ice', in which the local moments mimic the frustration of hydrogen ion positions in frozen water. Here we report an artificial geometrically frustrated magnet based on an array of lithographically fabricated single-domain ferromagnetic islands. The islands are arranged such that the dipole interactions create a two-dimensional analogue to spin ice. Images of the magnetic moments of individual elements in this correlated system allow us to study the local accommodation of frustration. We see both ice-like short-range correlations and an absence of long-range correlations, behaviour which is strikingly similar to the low-temperature state of spin ice. These results demonstrate that artificial frustrated magnets can provide an uncharted arena in which the physics of frustration can be directly visualized.
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Affiliation(s)
- R F Wang
- Department of Physics and Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA
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39
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Olayo-Valles R, Guo S, Lund MS, Leighton C, Hillmyer MA. Perpendicular Domain Orientation in Thin Films of Polystyrene−Polylactide Diblock Copolymers. Macromolecules 2005. [DOI: 10.1021/ma0509006] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Roberto Olayo-Valles
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, and Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455
| | - Shouwu Guo
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, and Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455
| | - M. S. Lund
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, and Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455
| | - C. Leighton
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, and Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455
| | - Marc A. Hillmyer
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, and Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455
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40
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Wang L, Umemoto K, Wentzcovitch RM, Chen TY, Chien CL, Checkelsky JG, Eckert JC, Dahlberg ED, Leighton C. Co1-xFexS2: a tunable source of highly spin-polarized electrons. Phys Rev Lett 2005; 94:056602. [PMID: 15783672 DOI: 10.1103/physrevlett.94.056602] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2004] [Indexed: 05/24/2023]
Abstract
In the emerging field of spin-electronics ideal ferromagnetic electron sources would not only possess a high degree of spin polarization, but would also offer control over the magnitude of this polarization. We demonstrate here that a simple scheme can be utilized to control both the magnitude and the sign of the spin polarization of ferromagnetic CoS2, which we probe with a variety of techniques. The position of the Fermi level is fine-tuned by solid solution alloying with the isostructural diamagnetic semiconductor FeS2, leading to tunable spin polarization of up to 85%.
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Affiliation(s)
- L Wang
- Department of Chemical Engineering and Materials Science, University of Minnesota, USA
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41
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Wu J, Lynn JW, Glinka CJ, Burley J, Zheng H, Mitchell JF, Leighton C. Intergranular giant magnetoresistance in a spontaneously phase separated perovskite oxide. Phys Rev Lett 2005; 94:037201. [PMID: 15698314 DOI: 10.1103/physrevlett.94.037201] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2004] [Indexed: 05/24/2023]
Abstract
We present small-angle neutron scattering data proving that, on the insulating side of the metal-insulator transition, the doped perovskite cobaltite La(1-x)Sr(x)CoO(3) phase separates into ferromagnetic metallic clusters embedded in a nonferromagnetic matrix. This induces a hysteretic magnetoresistance, with temperature and field dependence characteristic of intergranular giant magnetoresistance (GMR). We argue that this system is a natural analog to the artificial structures fabricated by depositing nanoscale ferromagnetic particles in a metallic or insulating matrix; i.e., this material displays a GMR effect without the deliberate introduction of chemical interfaces.
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Affiliation(s)
- J Wu
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
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Olayo-Valles R, Lund MS, Leighton C, Hillmyer MA. Large area nanolithographic templates by selective etching of chemically stained block copolymer thin films. ACTA ACUST UNITED AC 2004. [DOI: 10.1039/b408639b] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Kuhns PL, Hoch MJR, Moulton WG, Reyes AP, Wu J, Leighton C. Magnetic phase separation in La1-xSrxCoO3 by 59Co nuclear magnetic resonance. Phys Rev Lett 2003; 91:127202. [PMID: 14525396 DOI: 10.1103/physrevlett.91.127202] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2003] [Indexed: 05/24/2023]
Abstract
59Co NMR measurements on La1-xSrxCoO3 reported here establish unequivocally, for the first time, the coexistence of ferromagnetic regions, spin-glass regions, and hole-poor low spin regions at all x values from 0.1 to 0.5. A zero external field NMR spectrum, which is assigned to the ferromagnetic regions, has a spectral shape that is nearly x independent at 1.9 K, as are the relaxation times, T1 and T2. The integrated spectral area increases rapidly with x up to x = 0.2 and then decreases slightly for larger x. In a field of 9.97 T, a narrow NMR line is observed at 102 MHz, identical to that found in x = 0 samples in previous work. The integrated intensity of this spectrum decreases rapidly with increasing x, and is ascribed to hole-poor low spin regions. Beneath this spectrum, a third broad line, with a peak at 100 MHz, is assigned to a spin- or cluster-glass-like phase.
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Affiliation(s)
- P L Kuhns
- National High Magnetic Field Laboratory, Tallahassee, Florida 32310, USA
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44
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Leighton C. Introducing Health Sector Reform and Priority Health Services. Health Reform Prior Serv 2002:1. [PMID: 12222162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/26/2023]
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Florenzano R, Weil K, Cruz C, Acuña J, Fullerton C, Muñiz C, Leighton C, Marambio M. Personalidad limítrofe, somatización, trauma y violencia infantil: un estudio empírico. ACTA ACUST UNITED AC 2002. [DOI: 10.4067/s0717-92272002000400005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Abstract
Scleroderma or systemic sclerosis is a rare condition with many clinical manifestations including Raynaud's phenomenon. As with many other rarely encountered diseases, drug therapy for scleroderma is often empirical with little evidence in the form of randomised controlled trials to aid drug choice. Raynaud's phenomenon has been recognised for well over 100 years. A considerable number of clinical trials in this area have demonstrated unequivocally the use of nifedipine as a gold standard. Large studies have also demonstrated the efficacy of iloprost. However, this drug is not as yet licensed for scleroderma in the UK or elsewhere. This presents an additional problem as information regarding the use and administration of unlicensed drugs is often sparse and post-marketing surveillance to assess safety is not routinely performed. When looking at the other distinct conditions encountered by a patient with scleroderma it becomes evident that trials are often retrospective or limited in patient numbers. Studies investigating the use of methotrexate, antithymocyte globulin and cyclophosphamide in patients with scleroderma have been very small and in some cases not well designed. The major work on penicillamine was a retrospective trial. Again these drugs are not licensed for use in scleroderma. Drug therapy for pulmonary hypertension secondary to scleroderma closely follows that outlined for primary pulmonary hypertension. In the US there is a patient registry for primary pulmonary hypertension that has enabled well designed, large-scale studies to demonstrate the benefits of epoprostenol in severe primary pulmonary hypertension. Hence, research in this area has progressed considerably over the last decade. Clearly, a considerable amount of work is being carried out to elucidate new treatment regimens for scleroderma, however, evaluation of these studies is proving to be a difficult process. Designated hospital centres for scleroderma (there are currently 2 in the UK), better markers of disease activity and methods to measure improvement or deterioration in affected organs, should enable research into aetiology, disease progression and treatment to be carried out on a larger scale resulting, hopefully, in more conclusive answers.
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Affiliation(s)
- C Leighton
- Pharmacy Department, Royal Free Hospital, London, England.
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Leighton C, Fitzsimmons MR, Yashar P, Hoffmann A, Nogués J, Dura J, Majkrzak CF, Schuller IK. Two-stage magnetization reversal in exchange biased bilayers. Phys Rev Lett 2001; 86:4394-4397. [PMID: 11328183 DOI: 10.1103/physrevlett.86.4394] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2000] [Indexed: 05/23/2023]
Abstract
MnF(2)/Fe bilayers exhibit asymmetric magnetization reversal that occurs by coherent rotation on one side of the loop and by nucleation and propagation of domain walls on the other side of the loop. Here, we show by polarized neutron reflectometry, magnetization, and magnetotransport measurements that for samples with good crystalline "quality" the rotation is a two-stage process, due to coherent rotation to a stable state perpendicular to the cooling field direction. The result is remarkably asymmetrically shaped hysteresis loops.
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Affiliation(s)
- C Leighton
- Physics Department, University of California-San Diego, La Jolla, California 92093-0319. USA
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Leighton C, Fisher B, Stitt L, Macdonald D, Bauman G, Cairncross J. The dose-volume interaction in adult supratentorial low-grade glioma: higher radiation dose is beneficial amongv patients with partial resection. Eur J Cancer 2001. [DOI: 10.1016/s0959-8049(01)80567-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Abruzzo GK, Gill CJ, Flattery AM, Kong L, Leighton C, Smith JG, Pikounis VB, Bartizal K, Rosen H. Efficacy of the echinocandin caspofungin against disseminated aspergillosis and candidiasis in cyclophosphamide-induced immunosuppressed mice. Antimicrob Agents Chemother 2000; 44:2310-8. [PMID: 10952573 PMCID: PMC90063 DOI: 10.1128/aac.44.9.2310-2318.2000] [Citation(s) in RCA: 135] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The in vivo efficacy of the echinocandin antifungal caspofungin acetate (caspofungin; MK-0991) was evaluated in models of disseminated aspergillosis and candidiasis in mice with cyclophosphamide (CY)-induced immunosuppression. Caspofungin is a 1, 3-beta-D-glucan synthesis inhibitor efficacious against a number of clinically relevant fungi including Aspergillus and Candida species. Models of CY-induced transient or chronic leukopenia were used with once daily administration of therapy initiated 24 h after microbial challenge. Caspofungin was effective in treating disseminated aspergillosis in mice that were transiently leukopenic (significant prolongation of survival at doses of > or =0.125 mg/kg of body weight and a 50% protective dose [PD(50)] of 0.245 mg/kg/day at 28 days after challenge) or chronically leukopenic (50 to 100% survival at doses of > or =0.5 mg/kg and PD(50)s ranging from 0.173 to 0.400 mg/kg/day). Caspofungin was effective in the treatment and sterilization of Candida infections in mice with transient leukopenia with a 99% effective dose based on reduction in log(10) CFU of Candida albicans/gram of kidneys of 0.119 mg/kg and 80 to 100% of the caspofungin-treated mice having sterile kidneys at caspofungin doses from 0.25 to 2.0 mg/kg. In Candida-infected mice with chronic leukopenia, caspofungin was effective at all dose levels tested (0.25 to 1.0 mg/kg), with the log(10) CFU of C. albicans/gram of kidneys of caspofungin-treated mice being significantly lower (>99% reduction) than that of sham-treated mice from day 4 to day 28 after challenge. Also, 70 to 100% of the caspofungin-treated, chronic leukopenic mice had sterile kidneys at caspofungin doses of 0.5 to 1.0 mg/kg from day 8 to 28 after challenge. Sterilization of Candida infections by caspofungin in the absence of host leukocytes provides compelling in vivo evidence for fungicidal activity against C. albicans. Further human clinical trials with caspofungin against serious fungal infections are in progress.
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Affiliation(s)
- G K Abruzzo
- Infectious Diseases, Merck Research Laboratories, Rahway, New Jersey 07065-0900, USA.
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