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Fung KLB, Colson C, Bryan J, Saayujya C, Mokkarala-Lopez J, Hartley A, Yousuf K, Kuo R, Lu Y, Fellows BD, Chandrasekharan P, Conolly SM. First Superferromagnetic Remanence Characterization and Scan Optimization for Super-Resolution Magnetic Particle Imaging. NANO LETTERS 2023; 23:1717-1725. [PMID: 36821385 PMCID: PMC10790312 DOI: 10.1021/acs.nanolett.2c04404] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Magnetic particle imaging (MPI) is a sensitive, high-contrast tracer modality that images superparamagnetic iron oxide nanoparticles, enabling radiation-free theranostic imaging. MPI resolution is currently limited by scanner and particle constraints. Recent tracers have experimentally shown 10× resolution and signal improvements with dramatically sharper M-H curves. Experiments show a dependence on interparticle interactions, conforming to literature definitions of superferromagnetism. We thus call our tracers superferromagnetic iron oxide nanoparticles (SFMIOs). While SFMIOs provide excellent signal and resolution, they exhibit hysteresis with non-negligible remanence and coercivity. We provide the first quantitative measurements of SFMIO remanence decay and reformation using a novel multiecho pulse sequence. We characterize MPI scanning with remanence decay and coercivity and describe an SNR-optimized pulse sequence for SFMIOs under human electromagnetic safety limitations. The resolution from SFMIOs could enable clinical MPI with 10× reduced scanner selection fields, reducing hardware costs by up to 100×.
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Affiliation(s)
- K L Barry Fung
- UC Berkeley-UCSF Graduate Group in Bioengineering, University of California Berkeley and University of California San Francisco, https://bioegrad.berkeley.edu/
| | - Caylin Colson
- UC Berkeley-UCSF Graduate Group in Bioengineering, University of California Berkeley and University of California San Francisco, https://bioegrad.berkeley.edu/
| | - Jacob Bryan
- Department of Bioengineering, University of California Berkeley, Berkeley, California 94720, United States
| | - Chinmoy Saayujya
- Department of Electrical Engineering and Computer Sciences, University of California Berkeley, Berkeley, California 94720, United States
| | - Javier Mokkarala-Lopez
- Department of Bioengineering, University of California Berkeley, Berkeley, California 94720, United States
| | - Allison Hartley
- Department of Bioengineering, University of California Berkeley, Berkeley, California 94720, United States
| | - Khadija Yousuf
- Department of Bioengineering, University of California Berkeley, Berkeley, California 94720, United States
| | - Renesmee Kuo
- Department of Bioengineering, University of California Berkeley, Berkeley, California 94720, United States
| | - Yao Lu
- Department of Bioengineering, University of California Berkeley, Berkeley, California 94720, United States
| | - Benjamin D Fellows
- Department of Bioengineering, University of California Berkeley, Berkeley, California 94720, United States
| | - Prashant Chandrasekharan
- Department of Bioengineering, University of California Berkeley, Berkeley, California 94720, United States
| | - Steven M Conolly
- Department of Bioengineering, University of California Berkeley, Berkeley, California 94720, United States
- Department of Electrical Engineering and Computer Sciences, University of California Berkeley, Berkeley, California 94720, United States
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2
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Tay ZW, Savliwala S, Hensley DW, Fung KLB, Colson C, Fellows BD, Zhou X, Huynh Q, Lu Y, Zheng B, Chandrasekharan P, Rivera-Jimenez SM, Rinaldi-Ramos CM, Conolly SM. Superferromagnetic Nanoparticles Enable Order-of-Magnitude Resolution & Sensitivity Gain in Magnetic Particle Imaging. SMALL METHODS 2021; 5:e2100796. [PMID: 34927972 PMCID: PMC8837195 DOI: 10.1002/smtd.202100796] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Indexed: 05/02/2023]
Abstract
Magnetic nanoparticles have many advantages in medicine such as their use in non-invasive imaging as a Magnetic Particle Imaging (MPI) tracer or Magnetic Resonance Imaging contrast agent, the ability to be externally shifted or actuated and externally excited to generate heat or release drugs for therapy. Existing nanoparticles have a gentle sigmoidal magnetization response that limits resolution and sensitivity. Here it is shown that superferromagnetic iron oxide nanoparticle chains (SFMIOs) achieve an ideal step-like magnetization response to improve both image resolution & SNR by more than tenfold over conventional MPI. The underlying mechanism relies on dynamic magnetization with square-like hysteresis loops in response to 20 kHz, 15 kAm-1 MPI excitation, with nanoparticles assembling into a chain under an applied magnetic field. Experimental data shows a "1D avalanche" dipole reversal of every nanoparticle in the chain when the applied field overcomes the dynamic coercive threshold of dipole-dipole fields from adjacent nanoparticles in the chain. Intense inductive signal is produced from this event resulting in a sharp signal peak. Novel MPI imaging strategies are demonstrated to harness this behavior towards order-of-magnitude medical image improvements. SFMIOs can provide a breakthrough in noninvasive imaging of cancer, pulmonary embolism, gastrointestinal bleeds, stroke, and inflammation imaging.
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Affiliation(s)
- Zhi Wei Tay
- Department of Bioengineering, 340 Hearst Memorial Mining Building, University of California Berkeley, Berkeley, CA, 94720-1762, USA
- Institute of Bioengineering and Bioimaging, Agency for Science, Technology and Research (A*STAR), #02-02 Helios Building, Singapore, 138667, Singapore
| | - Shehaab Savliwala
- Department of Chemical Engineering, University of Florida, Gainesville, FL, 32611-6005, USA
| | - Daniel W Hensley
- Department of Bioengineering, 340 Hearst Memorial Mining Building, University of California Berkeley, Berkeley, CA, 94720-1762, USA
| | - K L Barry Fung
- Department of Bioengineering, 340 Hearst Memorial Mining Building, University of California Berkeley, Berkeley, CA, 94720-1762, USA
| | - Caylin Colson
- Department of Bioengineering, 340 Hearst Memorial Mining Building, University of California Berkeley, Berkeley, CA, 94720-1762, USA
| | - Benjamin D Fellows
- Department of Bioengineering, 340 Hearst Memorial Mining Building, University of California Berkeley, Berkeley, CA, 94720-1762, USA
| | - Xinyi Zhou
- Department of Bioengineering, 340 Hearst Memorial Mining Building, University of California Berkeley, Berkeley, CA, 94720-1762, USA
| | - Quincy Huynh
- Department of Bioengineering, 340 Hearst Memorial Mining Building, University of California Berkeley, Berkeley, CA, 94720-1762, USA
| | - Yao Lu
- Department of Bioengineering, 340 Hearst Memorial Mining Building, University of California Berkeley, Berkeley, CA, 94720-1762, USA
| | - Bo Zheng
- Department of Bioengineering, 340 Hearst Memorial Mining Building, University of California Berkeley, Berkeley, CA, 94720-1762, USA
| | - Prashant Chandrasekharan
- Department of Bioengineering, 340 Hearst Memorial Mining Building, University of California Berkeley, Berkeley, CA, 94720-1762, USA
| | | | - Carlos M Rinaldi-Ramos
- Department of Chemical Engineering, University of Florida, Gainesville, FL, 32611-6005, USA
| | - Steven M Conolly
- Department of Bioengineering, 340 Hearst Memorial Mining Building, University of California Berkeley, Berkeley, CA, 94720-1762, USA
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Costanzo S, Ngo AT, Russier V, Albouy PA, Simon G, Colomban P, Salzemann C, Richardi J, Lisiecki I. Enhanced structural and magnetic properties of fcc colloidal crystals of cobalt nanoparticles. NANOSCALE 2020; 12:24020-24029. [PMID: 33245306 DOI: 10.1039/d0nr05517d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We report the elaboration of supercrystals made up of dodecanoic acid-coated 8.1 nm-Co nanocrystals with controlled supercrystallinity, morphology and magnetic properties. Supercrystal growth is controlled using a solvent-mediated ligand-ligand interaction strategy. Either face-centered cubic supercrystalline films or single colloidal crystals composed of cobalt nanocrystals are obtained. The change in supercrystal morphology is explained by Flory-type solvation theory using Hansen solubility colloidal parameters. The use of the same batch of Co nanocrystals for the fabrication of supercrystalline films and colloidal crystals enables accurate comparative structural and magnetic studies using (high-resolution) transmission electron microscopy, field emission gun scanning electron microscopy, grazing incidence small-angle X-ray scattering and vibrating sample magnetometry. The nearest neighbor distance between nanoparticles is interpreted using theoretical models proposed in the literature. We evidence the increase in both geometric anisotropy and magnetic dipolar interactions for colloidal crystals compared to supercrystalline films.
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Affiliation(s)
- S Costanzo
- Sorbonne Université, CNRS, De la Molécule aux Nano-Objets: Réactivité, Interactions Spectroscopies, MONARIS, 75005, Paris, France.
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Dudek MR, Dudek KK, Wolak W, Wojciechowski KW, Grima JN. Magnetocaloric materials with ultra-small magnetic nanoparticles working at room temperature. Sci Rep 2019; 9:17607. [PMID: 31772197 PMCID: PMC6879751 DOI: 10.1038/s41598-019-53617-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Accepted: 11/02/2019] [Indexed: 11/21/2022] Open
Abstract
Through the use of the Monte Carlo simulations utilising the mean-field approach, we show that a dense assembly of separated ultra-small magnetic nanoparticles embedded into a non-magnetic deformable matrix can be characterized by a large isothermal magnetic entropy change even upon applying a weak magnetic field with values much smaller than one Tesla. We also show that such entropy change may be very significant in the vicinity of the room temperature which effect normally requires an application of a strong external magnetic field. The deformable matrix chosen in this work as a host for magnetic nanoparticles adopts a thin film form with a large surface area to volume ratio. This in turn in combination with a strong magneto-volume coupling exhibited by this material allows us to show its suitability to be used in the case of a variety of applications utilising local cooling/heating such as future magnetic refrigerants.
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Affiliation(s)
- M R Dudek
- Institute of Physics, University of Zielona Gora, ul. Szafrana 4a, 65-069, Zielona Gora, Poland.
| | - K K Dudek
- Institute of Physics, University of Zielona Gora, ul. Szafrana 4a, 65-069, Zielona Gora, Poland
| | - W Wolak
- Institute of Physics, University of Zielona Gora, ul. Szafrana 4a, 65-069, Zielona Gora, Poland
| | - K W Wojciechowski
- Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, 60-179, Poznan, Poland
| | - J N Grima
- Metamaterials Unit, Faculty of Science, University of Malta, Msida, MSD 2080, Malta
- Department of Chemistry, Faculty of Science, University of Malta, Msida, MSD 2080, Malta
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Wetegrove M, Witte K, Bodnar W, Pfahl DE, Springer A, Schell N, Westphal F, Burkel E. Formation of maghemite nanostructures in polyol: tuning the particle size via the precursor stoichiometry. CrystEngComm 2019. [DOI: 10.1039/c8ce02115e] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Investigating the polyol-assisted synthesis of maghemite nanoflowers, a strong impact of the iron precursor stoichiometry on physical properties is found.
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Affiliation(s)
| | - Kerstin Witte
- University of Rostock
- Institute of Physics
- 18059 Rostock
- Germany
| | - Wiktor Bodnar
- INP Leibniz Institute for Plasma Science and Technology
- 17489 Greifswald
- Germany
| | - Dan-Eric Pfahl
- University of Rostock
- Institute of Physics
- 18059 Rostock
- Germany
| | - Armin Springer
- University Medicine Rostock
- Medical Biology and Electron Microscopy Centre
- 18057 Rostock
- Germany
| | - Norbert Schell
- Helmholtz Centre Geesthacht
- Institute of Materials Research
- 21502 Geesthacht
- Germany
| | | | - Eberhard Burkel
- University of Rostock
- Institute of Physics
- 18059 Rostock
- Germany
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6
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Kulkarni SA, Kolhatkar AG, Lee TR, Garno JC. Vibrational response of clusters of Fe 3O 4 nanoparticles patterned on glass surfaces investigated with magnetic sample modulation AFM. NANOSCALE 2018; 10:20426-20434. [PMID: 30378633 DOI: 10.1039/c8nr06174b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The vibration of Fe3O4 nanoparticles in response to an alternating magnetic field can be sensitively detected using contact mode atomic force microscopy (AFM) combined with selective modulation of magnetic domains. While imaging patterned samples of magnetic nanoparticles with contact mode AFM, a magnetic field was applied to drive sample vibration. The field altered in polarity and strength according to parameters of an AC current applied to a solenoid located under the sample. The vibration of Fe3O4 nanoparticles was detected by a nonmagnetic AFM tip to map the changes in frequency and amplitude of the vibrating sample at the level of individual Fe3O4 nanoparticles and clusters. Colloidal lithography, was used to prepare patterns of Fe3O4 nanoparticles on a glass surface using the basic steps of mixing, drying and removing the surface template of latex spheres. Monodisperse latex spheres were used to guide the deposition of magnetic nanoparticles in the spaces between the close-packed spheres of the latex film. With a mixture approach of "two-particle" lithography, 2D arrays of patterned aggregates of metal nanoparticles were generated which formed a periodic, well-defined arrangement that was suitable for subsequent characterizations with magnetic sample modulation (MSM).
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Affiliation(s)
- Shalaka A Kulkarni
- Department of Chemistry, Louisiana State University, 232 Choppin Hall, Baton Rouge, LA, 70803 USA.
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7
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Kuzmann E, Stichleutner S, Homonnay Z, Havancsák K, Chisholm C, El-Sharif M, Skuratov V, Nakanishi A, Nomura K. Generation of superparamagnetism in metallic α-iron by swift heavy ion irradiation. Radiat Phys Chem Oxf Engl 1993 2016. [DOI: 10.1016/j.radphyschem.2016.06.032] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Botez CE, Morris JL. Ac-susceptibility investigations of superspin blocking and freezing in interacting magnetic nanoparticle ensembles. NANOTECHNOLOGY 2016; 27:115706. [PMID: 26876797 DOI: 10.1088/0957-4484/27/11/115706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We have investigated the effect of dipolar interactions on the superspin blocking and freezing of 9 nm average size Fe3O4 magnetic nanoparticle ensembles. Our dynamic susceptibility data reveals a two-regime behavior of the blocking temperature, T(B), upon diluting a Fe3O4/hexane magnetic fluid. As the nanoparticle volume ratio, Φ, is reduced from an as-prepared reference Φ = 1 to Φ = 1/96, the blocking temperature decreases from 46.1 K to 34.2 K, but higher values reenter upon further diluting the magnetic fluid to Φ = 1/384 (where T(B) = 42.5 K). We found evidence that cooling below T B within the higher concentration range (Φ > 1/48) leads to the collective freezing of the superspins, whereas individual superspin blocking occurs in the presence of weaker interactions (Φ < 1/96). The unexpected increase of the blocking temperature with the decrease of the inter-particle interactions observed at low nanoparticle concentrations is well described by the Mørup-Tronc model.
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Affiliation(s)
- Cristian E Botez
- Department of Physics, University of Texas at El Paso, 500 W. University Avenue, El Paso, TX 79968, USA
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9
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Chen C, Kukkadapu R, Sparks DL. Influence of Coprecipitated Organic Matter on Fe2+(aq)-Catalyzed Transformation of Ferrihydrite: Implications for Carbon Dynamics. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2015; 49:10927-36. [PMID: 26260047 DOI: 10.1021/acs.est.5b02448] [Citation(s) in RCA: 106] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Aqueous Fe(II) is known to catalyze the abiotic transformation of ferrihydrite to more stable Fe minerals. However, little is known about the impacts of coprecipitated OM on Fe(II)-catalyzed ferrihydrite transformation and its consequences for C dynamics. Accordingly, we investigated the extent and pathway of Fe(II)-induced transformation of OM-ferrihydrite coprecipitates as a function of C/Fe ratios and aqueous Fe(II) concentrations, and its implications for subsequent C dynamics. The coprecipitated OM resulted in a linear decrease in ferrihydrite transformation with increasing C/Fe ratios. The secondary mineral profiles upon Fe(II) reaction with OM-ferrihydrite coprecipitates depend on Fe(II) concentrations At 0.2 mM Fe(II), OM completely inhibited goethite formation and stimulated lepidocrocite formation. At 2 mM Fe(II), whereas goethite was formed in the presence of OM, OM reduced the amount of goethite and magnetite formation and increased the formation of lepidocrocite. The solid-phase C content remained unchanged after reaction, suggesting that OM remains associated with Fe minerals following ferrihydrite transformation to more stable Fe minerals. However, C desorbability by H2PO4(-) from the resulting Fe minerals following reaction was enhanced. The study indicates a "lepidocrocite favoring effect" by OM and suggests that Fe(II)-catalyzed transformation of ferrihydrite may decrease OM stability in natural environments under moderately reducing conditions.
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Affiliation(s)
- Chunmei Chen
- Department of Plant and Soil Sciences, Delaware Environmental Institute, University of Delaware , Newark, Delaware 19711, United States
| | - Ravi Kukkadapu
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory , Richland, Washington 99354, United States
| | - Donald L Sparks
- Department of Plant and Soil Sciences, Delaware Environmental Institute, University of Delaware , Newark, Delaware 19711, United States
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10
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Ghosh S, Puri IK. Changing the magnetic properties of microstructure by directing the self-assembly of superparamagnetic nanoparticles. Faraday Discuss 2015; 181:423-35. [PMID: 25941973 DOI: 10.1039/c4fd00245h] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Magnetic nanoparticles (MNPs) in a liquid dispersion can be organized through controlled self-assembly by applying an external magnetic field that regulates inter-particle interactions. Thus, micro- and nanostructures of desired morphology and superlattice geometry that show emergent magnetic properties can be fabricated. We describe how superferromagnetism, which is a specific type of emergence, can be produced. Here, superparamagnetic nanoparticles that show no individual residual magnetization are organized into structures with substantial residual magnetization that behave as miniature permanent magnets. We investigate the emergence of superferromagnetism in an idealized system consisting of two MNPs, by considering the influence that interparticle magnetostatic interactions have on the dynamics of the magnetic moments. We use this model to illustrate the design principles for self-assembly in terms of the choice of material and MNP particle size. We simulate the dynamics of the interacting magnetic moments by applying the stochastic Landau-Lifshitz-Gilbert equation to verify our principles. The findings enable a method to pattern material magnetization with submicron resolution, a useful feature that has potential applications for magnetic recording and microfluidic particle traps. The analysis also yields useful empirical generalizations that could facilitate other theoretical developments.
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Affiliation(s)
- Suvojit Ghosh
- Department of Engineering Physics, McMaster University, Hamilton, Ontario, Canada.
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11
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Gojdka B, Hrkac V, Strunskus T, Zaporojtchenko V, Kienle L, Faupel F. Study of cobalt clusters with very narrow size distribution deposited by high-rate cluster source. NANOTECHNOLOGY 2011; 22:465704. [PMID: 22025057 DOI: 10.1088/0957-4484/22/46/465704] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Co nanoparticles with an average diameter of 4.8 nm and a very narrow size distribution were prepared in a self-built gas aggregation cluster source without a size-selective filtering system. Ferromagnetic nanoparticle films with a thickness of several hundreds of nanometres were prepared at deposition rates up to 600 nm min(-1). Cluster properties and deposition characteristics were investigated for different deposition parameters. The as-deposited films exhibit high porosity compared to conventionally DC-sputtered films.
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Affiliation(s)
- B Gojdka
- Institute for Materials Science-Multicomponent Materials, Faculty of Engineering, Christian-Albrechts-University of Kiel, Kaiserstraße 2, D-24143 Kiel, Germany
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12
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Luis F, Campo J, Gómez J, McIntyre GJ, Luzón J, Ruiz-Molina D. Long-range ferromagnetism of Mn12 acetate single-molecule magnets under a transverse magnetic field. PHYSICAL REVIEW LETTERS 2005; 95:227202. [PMID: 16384259 DOI: 10.1103/physrevlett.95.227202] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2005] [Revised: 05/23/2005] [Indexed: 05/05/2023]
Abstract
We use neutron diffraction to probe the magnetization components of a crystal of Mn12 single-molecule magnets. Each of these molecules behaves, at low temperatures, as a nanomagnet with spin S = 10 and strong anisotropy along the crystallographic c axis. The application of a magnetic field H(perpendicular) perpendicular to c induces quantum tunneling between opposite spin orientations, enabling the spins to attain thermal equilibrium. For T approximately < 0.9(1) K, this equilibrium state shows spontaneous magnetization, indicating the onset of ferromagnetism. These long-range magnetic correlations nearly disappear for mu0H(perpendicular) approximately > 5.5 T, possibly suggesting the existence of a quantum critical point.
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Affiliation(s)
- F Luis
- Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza, 50009 Zaragoza, Spain.
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Peng DL, Sumiyama K, Yamamuro S, Hihara T, Konno TJ. Preparation and Magnetic Properties of Oxide-Coated Monodispersive Co Cluster Assembly. ACTA ACUST UNITED AC 1999. [DOI: 10.1002/(sici)1521-396x(199903)172:1<209::aid-pssa209>3.0.co;2-v] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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15
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Yamamuro S, Sumiyama K, Konno TJ, Suzuki K. Structural and Magnetic Evolution in Self-Assembling Process of Nanometer-Sized Co Clusters. ACTA ACUST UNITED AC 1999. [DOI: 10.2320/matertrans1989.40.1450] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Affiliation(s)
| | | | | | - Kenji Suzuki
- Institute for Materials Research, Tohoku University
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16
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Zhao J, Huggins FE, Feng Z, Huffman GP. Surface-induced superparamagnetic relaxation in nanoscale ferrihydrite particles. PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 54:3403-3407. [PMID: 9986240 DOI: 10.1103/physrevb.54.3403] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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17
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Richards HL, Novotny MA, Rikvold PA. Analytical and computational study of magnetization switching in kinetic Ising systems with demagnetizing fields. PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 54:4113-4127. [PMID: 9986314 DOI: 10.1103/physrevb.54.4113] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Morup S, Bodker F, Hendriksen PV, Linderoth S. Spin-glass-like ordering of the magnetic moments of interacting nanosized maghemite particles. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 52:287-294. [PMID: 9979603 DOI: 10.1103/physrevb.52.287] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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