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Wang K, Liu L, Pan H, Liu Z, Wang Y, Wang C, Zhao J, Chen J, Guo J. Antiferromagnetic Chromium-Doped Tin Clusters. J Phys Chem A 2024; 128:2737-2742. [PMID: 38566323 DOI: 10.1021/acs.jpca.4c00015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
The trend toward further miniaturization of micronano antiferromagnetic (AFM) spintronic devices has led to a strong demand for low-dimensional materials. The assembly of AFM clusters to produce such materials is a potential pathway that promotes studies on such clusters. In this work, we report on the discovery of the AFM Cr2Snx (x = 3-20) clusters with a stepwise growth at the density functional theory (DFT) level. In comparison, the two Cr atoms tend to stay together and be buried by Sn atoms, forming endohedral structures with one Cr atom encapsulated at size 9 and finally forming a full-encapsulated structure at size 17. Each successive cluster size is composed of its predecessor with an extra Sn atom adsorbed onto the face, giving evidence of stepwise growth. All these Cr2Snx (x = 3-20) clusters are antiferromagnets, except for the triplet-state ferrimagnetic Cr2Sn11, and all their singly negatively and positively charged ions are ferromagnets. The found stable Cr2Sn17 cluster can dimerize, yielding dimers and trimers without noticeably distorting the geometrical structure and magnetic properties of each of its constituent cluster monomers, making it possible as a building block for AFM materials.
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Affiliation(s)
- Kai Wang
- Henan Engineering Research Centre of Building-Photovoltaics, School of Mathematics and Physics, Henan University of Urban Construction, Pingdingshan 467036, China
| | - Le Liu
- Henan Engineering Research Centre of Building-Photovoltaics, School of Mathematics and Physics, Henan University of Urban Construction, Pingdingshan 467036, China
| | - Hui Pan
- Henan Engineering Research Centre of Building-Photovoltaics, School of Mathematics and Physics, Henan University of Urban Construction, Pingdingshan 467036, China
| | - Zhiqing Liu
- Henan Engineering Research Centre of Building-Photovoltaics, School of Mathematics and Physics, Henan University of Urban Construction, Pingdingshan 467036, China
| | - Yarui Wang
- Henan Engineering Research Centre of Building-Photovoltaics, School of Mathematics and Physics, Henan University of Urban Construction, Pingdingshan 467036, China
| | - Chaoyong Wang
- Henan Engineering Research Centre of Building-Photovoltaics, School of Mathematics and Physics, Henan University of Urban Construction, Pingdingshan 467036, China
| | - Jun Zhao
- Henan Engineering Research Centre of Building-Photovoltaics, School of Mathematics and Physics, Henan University of Urban Construction, Pingdingshan 467036, China
| | - Jiaye Chen
- Henan Engineering Research Centre of Building-Photovoltaics, School of Mathematics and Physics, Henan University of Urban Construction, Pingdingshan 467036, China
| | - Junji Guo
- Henan Engineering Research Centre of Building-Photovoltaics, School of Mathematics and Physics, Henan University of Urban Construction, Pingdingshan 467036, China
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Navrátil J, Błoński P, Otyepka M. Large magnetic anisotropy in an OsIr dimer anchored in defective graphene. NANOTECHNOLOGY 2021; 32:230001. [PMID: 33626515 DOI: 10.1088/1361-6528/abe966] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 02/24/2021] [Indexed: 06/12/2023]
Abstract
Single-atom magnets represent the ultimate limit of magnetic data storage. The identification of substrates that anchor atom-sized magnets firmly and, thus, prevent their diffusion and large magnetic anisotropy has been at the centre of intense research efforts for a long time. Using density functional theory we show the binding of transition metal (TM) atoms in defect sites in the graphene lattice: single vacancy and double vacancy, both pristine and decorated by pyridinic nitrogen atoms, are energetically more favourable than away from the centre of defects, which could be used for engineering the position of TMs with atomic precision. Relativistic calculations revealed magnetic anisotropy energy (MAE) of ∼10 meV for Ir@NSV with an easy axis parallel to the graphene plane. MAE can be remarkably boosted to 50 meV for OsIr@NSV with the easy axis perpendicular to the graphene plane, which paves the way to the storage density of ∼490 Tb/inch2with the blocking temperature of 14 K assuming the relaxation time of 10 years. Magnetic anisotropy is discussed based on the relativistic electronic structures. The influence of an orbital-dependent on-site Coulomb repulsionUand a non-local correlation functional optB86b-vdW on MAE is also discussed.
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Affiliation(s)
- Jan Navrátil
- Department of Physical Chemistry, Faculty of Science, Palacký University Olomouc, tř. 17 listopadu 12, 771 46 Olomouc, Czech Republic
| | - Piotr Błoński
- Regional Centre of Advanced Technologies and Materials, Faculty of Science, Palacký University Olomouc, Šlechtitelů 27, 783 71 Olomouc, Czech Republic
| | - Michal Otyepka
- Regional Centre of Advanced Technologies and Materials, Faculty of Science, Palacký University Olomouc, Šlechtitelů 27, 783 71 Olomouc, Czech Republic
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Zhang W, Wong PKJ, Zhou X, Rath A, Huang Z, Wang H, Morton SA, Yuan J, Zhang L, Chua R, Zeng S, Liu E, Xu F, Chua DHC, Feng YP, van der Laan G, Pennycook SJ, Zhai Y, Wee ATS. Ferromagnet/Two-Dimensional Semiconducting Transition-Metal Dichalcogenide Interface with Perpendicular Magnetic Anisotropy. ACS NANO 2019; 13:2253-2261. [PMID: 30775909 DOI: 10.1021/acsnano.8b08926] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Ferromagnet/two-dimensional transition-metal dichalcogenide (FM/2D TMD) interfaces provide attractive opportunities to push magnetic information storage to the atomically thin limit. Existing work has focused on FMs contacted with mechanically exfoliated or chemically vapor-deposition-grown TMDs, where clean interfaces cannot be guaranteed. Here, we report a reliable way to achieve contamination-free interfaces between ferromagnetic CoFeB and molecular-beam epitaxial MoSe2. We show a spin reorientation arising from the interface, leading to a perpendicular magnetic anisotropy (PMA), and reveal the CoFeB/2D MoSe2 interface allowing for the PMA development in a broader CoFeB thickness-range than common systems such as CoFeB/MgO. Using X-ray magnetic circular dichroism analysis, we attribute generation of this PMA to interfacial d-d hybridization and deduce a general rule to enhance its magnitude. We also demonstrate favorable magnetic softness and considerable magnetic moment preserved at the interface and theoretically predict the interfacial band matching for spin filtering. Our work highlights the CoFeB/2D MoSe2 interface as a promising platform for examination of TMD-based spintronic applications and might stimulate further development with other combinations of FM/2D TMD interfaces.
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Affiliation(s)
- Wen Zhang
- Department of Physics , National University of Singapore , 2 Science Drive 3 , Singapore 117542 , Singapore
| | - Ping Kwan Johnny Wong
- Centre for Advanced 2D Materials and Graphene Research Centre , National University of Singapore , 6 Science Drive 2 , Singapore 117546 , Singapore
| | - Xiaochao Zhou
- School of Physics , Southeast University , Nanjing 211189 , China
| | - Ashutosh Rath
- Department of Materials Science and Engineering , National University of Singapore , Singapore 117575 , Singapore
| | - Zhaocong Huang
- School of Physics , Southeast University , Nanjing 211189 , China
| | - Hongyu Wang
- Department of Materials Science and Engineering , National University of Singapore , Singapore 117575 , Singapore
| | - Simon A Morton
- Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Jiaren Yuan
- Department of Physics , National University of Singapore , 2 Science Drive 3 , Singapore 117542 , Singapore
| | - Lei Zhang
- Department of Physics , National University of Singapore , 2 Science Drive 3 , Singapore 117542 , Singapore
| | - Rebekah Chua
- Department of Physics , National University of Singapore , 2 Science Drive 3 , Singapore 117542 , Singapore
- NUS Graduate School for Integrative Sciences and Engineering , National University of Singapore , Centre for Life Sciences, #05-01, 28 Medical Drive , Singapore 117456 Singapore
| | - Shengwei Zeng
- Department of Physics , National University of Singapore , 2 Science Drive 3 , Singapore 117542 , Singapore
- NUSSNI-NanoCore , National University of Singapore , 5A Engineering Drive 1 , Singapore 117411 , Singapore
| | - Er Liu
- School of Materials Science and Engineering , Nanjing University of Science and Technology , Nanjing 210094 , China
| | - Feng Xu
- School of Materials Science and Engineering , Nanjing University of Science and Technology , Nanjing 210094 , China
| | - Daniel H C Chua
- Department of Materials Science and Engineering , National University of Singapore , Singapore 117575 , Singapore
| | - Yuan Ping Feng
- Department of Physics , National University of Singapore , 2 Science Drive 3 , Singapore 117542 , Singapore
| | | | - Stephen J Pennycook
- Centre for Advanced 2D Materials and Graphene Research Centre , National University of Singapore , 6 Science Drive 2 , Singapore 117546 , Singapore
- Department of Materials Science and Engineering , National University of Singapore , Singapore 117575 , Singapore
| | - Ya Zhai
- School of Physics , Southeast University , Nanjing 211189 , China
| | - Andrew T S Wee
- Department of Physics , National University of Singapore , 2 Science Drive 3 , Singapore 117542 , Singapore
- Centre for Advanced 2D Materials and Graphene Research Centre , National University of Singapore , 6 Science Drive 2 , Singapore 117546 , Singapore
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4
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Abstract
We have prepared a set of polycrystalline samples of La 0.8 Sr 0.2 Co 1 − x Al x O 3 ( 0 ≤ x ≤ 0.2 ), and have measured the magnetization as functions of temperature and magnetic field. We find that the average spin number per Co ion ( S Co ) evaluated from the room-temperature susceptibility is around 1.2–1.3 and independent of x. However, we further find that S Co evaluated from the saturation magnetization at 2 K is around 0.3–0.7, and decreases dramatically with x. This naturally indicates that a significant fraction of the Co 3 + ions experience a spin-state crossover from the intermediate- to low-spin state with decreasing temperature in the Al-substituted samples. This spin-state crossover also explains the resistivity and the thermopower consistently. In particular, we find that the thermopower is anomalously enhanced by the Al substitution, which can be consistently explained in terms of an extended Heikes formula.
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Wang P, Jiang X, Hu J, Huang X, Zhao J, Ahuja R. Prediction of huge magnetic anisotropies in 5d transition metallocenes. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:435802. [PMID: 28825594 DOI: 10.1088/1361-648x/aa8755] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The stability, electronic structure and non-collinear magnetic properties of a series of 5d metallocenes, namely, two cyclopentadienyl (Cp) rings sandwiched with a single 5d transition metal atom, are investigated. Our first-principles calculations reveal that Cp rings not only provide a suitable ligand environment for metal atoms, but also result in tunable magnetism depending on the transition metal element. Among them, HfCp2 and WCp2 show a high preference for the magnetization axis perpendicular to the Cp plane, with large magnetic anisotropy energies (MAEs) around 10 meV. We further consider triple decker metallocenes (M2Cp3), and find a huge MAE of above 60 meV in Ta2Cp3. The orbital energy split and shifts induced by composition change in metallocenes is mainly responsible for the significant MAE enhancement. By choosing a suitable crystal field for transition metal atoms, we pave a feasible pathway for designing promising building blocks of future magnetic storage devices.
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Affiliation(s)
- Peng Wang
- Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Dalian University of Technology, Ministry of Education, Dalian 116024, People's Republic of China
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Formation and evolution of orientation-specific CO 2 chains on nonpolar ZnO(10͞10) surfaces. Sci Rep 2017; 7:43442. [PMID: 28262810 PMCID: PMC5473178 DOI: 10.1038/srep43442] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Accepted: 01/23/2017] [Indexed: 11/08/2022] Open
Abstract
Clarifying the fundamental adsorption and diffusion process of CO2 on single crystal ZnO surfaces is critical in understanding CO2 activation and transformation over ZnO-based catalysts. By using ultrahigh vacuum-Fourier transform infrared spectroscopy (UHV-FTIRS), we observed the fine structures of CO2 vibrational bands on ZnO(100) surfaces, which are the combinations of different vibrational frequencies, originated from CO2 monomer, dimer, trimer and longer polymer chains along [0001] direction according to the density functional theory calculations. Such novel chain adsorption mode results from the relatively large attractive interaction between CO2 and Zn3c atoms in [0001] direction. Further experiments indicate that the short chains at low coverage evolve into long chains through Ostwald ripening by annealing. At higher CO2 coverage (0.7 ML), the as-grown local (2 × 1) phase of chains first evolve into an unstable local (1 × 1) phase below 150 K, and then into a stable well-defined (2 × 1) phase above 150 K.
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7
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Zhao X, Shao X, Fujimori Y, Bhattacharya S, Ghiringhelli LM, Freund HJ, Sterrer M, Nilius N, Levchenko SV. Formation of Water Chains on CaO(001): What Drives the 1D Growth? J Phys Chem Lett 2015; 6:1204-1208. [PMID: 26262972 DOI: 10.1021/acs.jpclett.5b00223] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Formation of partly dissociated water chains is observed on CaO(001) films upon water exposure at 300 K. While morphology and orientation of the 1D assemblies are revealed from scanning tunneling microscopy, their atomic structure is identified with infrared absorption spectroscopy combined with density functional theory calculations. The latter exploit an ab initio genetic algorithm linked to atomistic thermodynamics to determine low-energy H2O configurations on the oxide surface. The development of 1D structures on the C4v symmetric CaO(001) is triggered by symmetry-broken water tetramers and a favorable balance between adsorbate-adsorbate versus adsorbate-surface interactions at the constraint of the CaO lattice parameter.
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Affiliation(s)
- Xunhua Zhao
- †Fritz-Haber-Institute, Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - Xiang Shao
- †Fritz-Haber-Institute, Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - Yuichi Fujimori
- †Fritz-Haber-Institute, Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - Saswata Bhattacharya
- †Fritz-Haber-Institute, Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - Luca M Ghiringhelli
- †Fritz-Haber-Institute, Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - Hans-Joachim Freund
- †Fritz-Haber-Institute, Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - Martin Sterrer
- †Fritz-Haber-Institute, Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
- §Institute of Physics, University of Graz, Universitaetsplatz 5, 8010 Graz, Austria
| | - Niklas Nilius
- †Fritz-Haber-Institute, Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
- ∥Institute of Physics, Carl-von-Ossieztky University, 26111 Oldenburg, Germany
| | - Sergey V Levchenko
- †Fritz-Haber-Institute, Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
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8
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Michez L, Chen K, Cheynis F, Leroy F, Ranguis A, Jamgotchian H, Hanbücken M, Masson L. Magnetic properties of self-organized Co dimer nanolines on Si/Ag(110). BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2015; 6:777-84. [PMID: 25977848 PMCID: PMC4419577 DOI: 10.3762/bjnano.6.80] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Accepted: 02/17/2015] [Indexed: 05/30/2023]
Abstract
We demonstrate the kinetically controlled growth of one-dimensional Co nanomagnets with a high lateral order on a nanopatterned Ag(110) surface. First, self-organized Si nanoribbons are formed upon submonolayer condensation of Si on the anisotropic Ag(110) surface. Depending on the growth temperature, individual or regular arrays (with a pitch of 2 nm) of Si nanoribbons can be grown. Next, the Si/Ag(110) system is used as a novel one-dimensional Si template to guide the growth of Co dimer nanolines on top of the Si nanoribbons, taking advantage of the fact that the thermally activated process of Co diffusion into the Si layer is efficiently hindered at 220 K. Magnetic characterization of the Co nanolines using X-ray magnetic circular dichroism reveals that the first atomic Co layer directly adsorbed onto the Si nanoribbons presents a weak magnetic response. However, the second Co layer exhibits an enhanced magnetization, strongly suggesting a ferromagnetic ordering with an in-plane easy axis of magnetization, which is perpendicular to the Co nanolines.
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Affiliation(s)
- Lisa Michez
- Aix Marseille Université, CNRS, CINaM UMR 7325, 13288 Marseille, France
| | - Kai Chen
- Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin – BP 48, 91192 Gif-sur-Yvette Cedex, France
| | - Fabien Cheynis
- Aix Marseille Université, CNRS, CINaM UMR 7325, 13288 Marseille, France
| | - Frédéric Leroy
- Aix Marseille Université, CNRS, CINaM UMR 7325, 13288 Marseille, France
| | - Alain Ranguis
- Aix Marseille Université, CNRS, CINaM UMR 7325, 13288 Marseille, France
| | - Haik Jamgotchian
- Aix Marseille Université, CNRS, CINaM UMR 7325, 13288 Marseille, France
| | - Margrit Hanbücken
- Aix Marseille Université, CNRS, CINaM UMR 7325, 13288 Marseille, France
| | - Laurence Masson
- Aix Marseille Université, CNRS, CINaM UMR 7325, 13288 Marseille, France
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9
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Joly L, Otero E, Choueikani F, Marteau F, Chapuis L, Ohresser P. Fast continuous energy scan with dynamic coupling of the monochromator and undulator at the DEIMOS beamline. JOURNAL OF SYNCHROTRON RADIATION 2014; 21:502-506. [PMID: 24763639 DOI: 10.1107/s1600577514003671] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2013] [Accepted: 02/18/2014] [Indexed: 06/03/2023]
Abstract
In order to improve the efficiency of X-ray absorption data recording, a fast scan method, the Turboscan, has been developed on the DEIMOS beamline at Synchrotron SOLEIL, consisting of a software-synchronized continuous motion of the monochromator and undulator motors. This process suppresses the time loss when waiting for the motors to reach their target positions, as well as software dead-time, while preserving excellent beam characteristics.
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Affiliation(s)
- L Joly
- Institut de Physique et de Chimie des Materiaux de Strasbourg, Université de Strasbourg, UMR 7504, 23 Rue du Loess, BP 43, 67034 Strasbourg Cedex 2, France
| | - E Otero
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette, France
| | - F Choueikani
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette, France
| | - F Marteau
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette, France
| | - L Chapuis
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette, France
| | - P Ohresser
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette, France
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10
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Brovko OO, Ruiz-Díaz P, Dasa TR, Stepanyuk VS. Controlling magnetism on metal surfaces with non-magnetic means: electric fields and surface charging. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:093001. [PMID: 24523356 DOI: 10.1088/0953-8984/26/9/093001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We review the state of the art of surface magnetic property control with non-magnetic means, concentrating on metallic surfaces and techniques such as charge-doping or external electric field (EEF) application. Magneto-electric coupling via EEF-based charge manipulation is discussed as a way to tailor single adatom spins, exchange interaction between adsorbates or anisotropies of layered systems. The mechanisms of paramagnetic and spin-dependent electric field screening and the effect thereof on surface magnetism are discussed in the framework of theoretical and experimental studies. The possibility to enhance the effect of EEF by immersing the target system into an electrolyte or ionic liquid is discussed by the example of substitutional impurities and metallic alloy multilayers. A similar physics is pointed out for the case of charge traps, metallic systems decoupled from a bulk electron bath. In that case the charging provides the charge carrier density changes necessary to affect the magnetic moments and anisotropies in the system. Finally, the option of using quasi-free electrons rather than localized atomic spins for surface magnetism control is discussed with the example of Shockley-type metallic surface states confined to magnetic nanoislands.
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Affiliation(s)
- Oleg O Brovko
- Max-Planck Institut für Mikrostrukturphysik, Halle, Germany
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11
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Ohresser P, Otero E, Choueikani F, Chen K, Stanescu S, Deschamps F, Moreno T, Polack F, Lagarde B, Daguerre JP, Marteau F, Scheurer F, Joly L, Kappler JP, Muller B, Bunau O, Sainctavit P. DEIMOS: a beamline dedicated to dichroism measurements in the 350-2500 eV energy range. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2014; 85:013106. [PMID: 24517744 DOI: 10.1063/1.4861191] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The DEIMOS (Dichroism Experimental Installation for Magneto-Optical Spectroscopy) beamline was part of the second phase of the beamline development at French Synchrotron SOLEIL (Source Optimisée de Lumière à Energie Intermédiaire du LURE) and opened to users in March 2011. It delivers polarized soft x-rays to perform x-ray absorption spectroscopy, x-ray magnetic circular dichroism, and x-ray linear dichroism in the energy range 350-2500 eV. The beamline has been optimized for stability and reproducibility in terms of photon flux and photon energy. The main end-station consists in a cryo-magnet with 2 split coils providing a 7 T magnetic field along the beam or 2 T perpendicular to the beam with a controllable temperature on the sample from 370 K down to 1.5 K.
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Affiliation(s)
- P Ohresser
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin - BP 48, 91192 Gif-sur-Yvette, France
| | - E Otero
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin - BP 48, 91192 Gif-sur-Yvette, France
| | - F Choueikani
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin - BP 48, 91192 Gif-sur-Yvette, France
| | - K Chen
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin - BP 48, 91192 Gif-sur-Yvette, France
| | - S Stanescu
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin - BP 48, 91192 Gif-sur-Yvette, France
| | - F Deschamps
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin - BP 48, 91192 Gif-sur-Yvette, France
| | - T Moreno
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin - BP 48, 91192 Gif-sur-Yvette, France
| | - F Polack
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin - BP 48, 91192 Gif-sur-Yvette, France
| | - B Lagarde
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin - BP 48, 91192 Gif-sur-Yvette, France
| | - J-P Daguerre
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin - BP 48, 91192 Gif-sur-Yvette, France
| | - F Marteau
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin - BP 48, 91192 Gif-sur-Yvette, France
| | - F Scheurer
- Institut de Physique et Chimie des Matériaux de Strasbourg, UMR 7504 UdS-CNRS, 67034 Strasbourg Cedex 2, France
| | - L Joly
- Institut de Physique et Chimie des Matériaux de Strasbourg, UMR 7504 UdS-CNRS, 67034 Strasbourg Cedex 2, France
| | - J-P Kappler
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin - BP 48, 91192 Gif-sur-Yvette, France
| | - B Muller
- Institut de Physique et Chimie des Matériaux de Strasbourg, UMR 7504 UdS-CNRS, 67034 Strasbourg Cedex 2, France
| | - O Bunau
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin - BP 48, 91192 Gif-sur-Yvette, France
| | - Ph Sainctavit
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin - BP 48, 91192 Gif-sur-Yvette, France
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12
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Tuning magnetic anisotropies of Fe films on Si(111) substrate via direction variation of heating current. Sci Rep 2013; 3:1547. [PMID: 23529097 PMCID: PMC3607890 DOI: 10.1038/srep01547] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2013] [Accepted: 03/08/2013] [Indexed: 11/30/2022] Open
Abstract
We adopted a novel method to tune the terrace width of Si(111) substrate by varying the direction of heating current. It was observed that the uniaxial magnetic anisotropy (UMA) of Fe films grown on the Si(111) substrate enhanced with decreasing the terrace width and superimposed on the weak six-fold magnetocrystalline anisotropy. Furthermore, on the basis of the scanning tunneling microscopy (STM) images, self-correlation function calculations confirmed that the UMA was attributed mainly from the long-range dipolar interaction between the spins on the surface. Our work opens a new avenue to manipulate the magnetic anisotropy of magnetic structures on the stepped substrate by the decoration of its atomic steps.
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13
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Ohresser P, Otero E, Choueikani F, Stanescu S, Deschamps F, Ibis L, Moreno T, Polack F, Lagarde B, Marteau F, Scheurer F, Joly L, Kappler JP, Muller B, Sainctavit P. Polarization characterization on the DEIMOS beamline using dichroism measurements. ACTA ACUST UNITED AC 2013. [DOI: 10.1088/1742-6596/425/21/212007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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14
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Arora SK, O'Dowd BJ, Ballesteros B, Gambardella P, Shvets IV. Magnetic properties of planar nanowire arrays of Co fabricated on oxidized step-bunched silicon templates. NANOTECHNOLOGY 2012; 23:235702. [PMID: 22595752 DOI: 10.1088/0957-4484/23/23/235702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Planar nanowire (NW) arrays of Co grown on oxidized step-bunched Si(111) templates exhibit room temperature ferromagnetic behaviour for wire widths down to 25 nm. Temperature and thickness dependent magnetization studies on these polycrystalline NW arrays show that the magnetic anisotropy of the NW array is dominated by shape anisotropy, which keeps the magnetization in-plane with easy axis parallel to the wires. This shape related uniaxial anisotropy is preserved even at low temperatures (10 K). Thickness dependent studies reveal that the magnetization reversal is governed by the curling mode reversal for thick wires whereas thinner wires exhibit a more complex behaviour which is related to thermal effects and size distribution of the crystal grains that constitute the NWs.
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Affiliation(s)
- S K Arora
- Centre for Research on Adaptive Nanostructures and Nanodevices and School of Physics, Trinity College Dublin, Dublin 2, Ireland.
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15
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Bauer DSG, Mavropoulos P, Lounis S, Blügel S. Thermally activated magnetization reversal in monatomic magnetic chains on surfaces studied by classical atomistic spin-dynamics simulations. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:394204. [PMID: 21921308 DOI: 10.1088/0953-8984/23/39/394204] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We analyse the spontaneous magnetization reversal of supported monatomic chains of finite length due to thermal fluctuations via atomistic spin-dynamics simulations. Our approach is based on the integration of the Landau-Lifshitz equation of motion of a classical spin Hamiltonian in the presence of stochastic forces. The associated magnetization lifetime is found to obey an Arrhenius law with an activation barrier equal to the domain wall energy in the chain. For chains longer than one domain wall width, the reversal is initiated by nucleation of a reversed magnetization domain primarily at the chain edge followed by a subsequent propagation of the domain wall to the other edge in a random-walk fashion. This results in a linear dependence of the lifetime on the chain length, if the magnetization correlation length is not exceeded. We studied chains of uniaxial and triaxial anisotropy and found that a triaxial anisotropy leads to a reduction of the magnetization lifetime due to a higher reversal attempt rate, even though the activation barrier is not changed.
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Affiliation(s)
- David S G Bauer
- Institut für Festkörperforschung, Institute for Advanced Simulation, and JARA, Forschungszentrum Jülich, D-52425 Jülich, Germany
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16
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Li F, Allegretti F, Surnev S, Netzer FP. Oxide-metal nanowires by oxidation of a one-dimensional Mn-Pd alloy: stability and reactivity. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:16474-16480. [PMID: 20527835 DOI: 10.1021/la101228s] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Distinct one-dimensional (1D) oxide nanowires decorating the step edges of a stepped Pd(1 1 9) surface are formed by partial and complete oxidation of a 1D Mn-Pd alloy. Under full postoxidation treatment at 470-570 K, 1D MnO(2) nanowires coupled pseudomorphically to the Pd steps are obtained. Oxidized nanowires, which maintain the basic structural pattern of the 1D Mn-Pd alloy, are instead prepared by exposure of the Mn-Pd alloy to O(2) at 90 K and subsequent short heating to 400 K. A relatively weak Mn-O bonding characterizes these oxidized alloy wires, which are readily reduced by reaction with CO at moderate temperature (350 K). The here reported system emphasizes the influence of kinetic constraints in the formation of oxide nanostructures.
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Affiliation(s)
- Fanghua Li
- Surface and Interface Physics, Institute of Physics, Karl-Franzens University A-8010 Graz, Austria
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17
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Błoński P, Hafner J. Density-functional theory of the magnetic anisotropy of nanostructures: an assessment of different approximations. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:426001. [PMID: 21715860 DOI: 10.1088/0953-8984/21/42/426001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We discuss the multiple technical choices that have to be made in ab initio density-functional calculations of the magnetic anisotropy of supported nanostructures: (i) choice of the exchange-correlation functional, (ii) degree of optimization of the geometry of the adsorbate/substrate complex, (iii) magnetic anisotropy energy calculated self-consistently or via the 'force theorem', (iv) calculations based on slab models of the substrate or using a Green's function describing a semi-infinite substrate, (v) full potential approach or atomic-sphere approximation. Using isolated Fe and Co atoms on Pt(111) as an example we demonstrate that by using a judicious combination of relatively crude approximations (complete neglect of structural relaxation, local exchange-correlation functional,...) seemingly good agreement with experimental anisotropy energies can be achieved, while the calculated orbital moments remain small. At a higher level of theory (relaxed adsorbate/substrate complex, gradient-corrected functionals,...) providing a realistic geometry of the adsorbate/substrate complex and hence a correct description of the interaction between the magnetic adatom and its ligands, anisotropy energies are also in semi-quantitative agreement with experiment, while the orbital moments of the adatoms are much too small. We suggest that the anisotropy energies provided by both approaches should be considered as lower limits of the real anisotropies. Without relaxation the ligand effect coupling the orbital moments of the adatom to the heavy atoms of the substrate is underestimated, while in a relaxed adsorbate/substrate complex the lack of orbital dependence of the exchange potential combined with a strong hybridization of adatom and substrate states leads to a strong underestimation of the orbital moment. We have briefly explored the influence of post-density-functional corrections. Adding a modest on-site Coulomb repulsion to the d states of the adatom (in a DFT+U approach) leads to a modest increase of spin and orbital moments of the adatom accompanied by a slow decrease of the induced moments, leaving the anisotropy energy almost unchanged.
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Affiliation(s)
- Piotr Błoński
- Fakultät für Physik and Center for Computational Materials Science, Universität Wien, Sensengasse 8/12, A-1090 Wien, Austria
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18
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Tegenkamp C. Vicinal surfaces for functional nanostructures. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:013002. [PMID: 21817211 DOI: 10.1088/0953-8984/21/1/013002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Vicinal surfaces are currently the focus of research. The regular arrangements of atomic steps on a mesoscopic scale reveal the possibility to functionalize these surfaces for technical applications, e.g. nanowires, catalysts, etc. The steps of the vicinal surface are well-defined defect structures of atomic size for nucleation of low-dimensional nanostructures. The concentration and therefore the coupling between the nanostructures can be tuned over a wide range by simply changing the inclination angle of the substrate. However, the coupling of these nano-objects to the substrate is just as important in controlling their electronic or chemical properties and making a functionality useable. On the basis of stepped insulating films, these aspects are fulfilled and will be considered in the first part of this review. Recent results for the epitaxial growth of wide bandgap insulating films (CaF(2), MgO, NaCl, BaSrO) on metallic and semiconducting vicinal substrates (Si(100), Ge(100), Ag(100)) will be presented. The change of the electronic structure, the adsorption behavior as well as the kinetics and energetics of color centers in the presence of steps is discussed. The successful bridging of the gap between the atomic and mesoscopic world, i.e. the functionalization of vicinal surfaces by nanostructures, is demonstrated in the second part by metal adsorption on semiconducting surfaces. For (sub)monolayer coverage these systems have in common that the surface states do not hybridize with the support, i.e. the semiconducting surfaces are insulating. Here I will focus on the latest results of macroscopic transport measurements on Pb quantum wires grown on vicinal Si(111) showing indeed a one-dimensional transport behavior.
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Affiliation(s)
- Christoph Tegenkamp
- Institut für Festkörperphysik, Gottfried Wilhelm Leibniz Universität Hannover, Appelstrasse 2, D-30167 Hannover, Germany
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Carroll L, Fleischer K, Cunniffe JP, McGilp JF. Magnetic second-harmonic generation from the terraces and steps of aligned magnetic nanostructures grown on low symmetry interfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2008; 20:265002. [PMID: 21694351 DOI: 10.1088/0953-8984/20/26/265002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Aligned magnetic nanostructures grown on low symmetry interfaces are generally inhomogeneous, with different magnetic species, such as terrace and step atoms, contributing to the overall magnetic response from the interfacial regions. It is shown that the presence of different magnetic regions can be detected by means of normal incidence (NI) magnetic second-harmonic generation (MSHG). A phenomenological model of NI MSHG at magnetic interfaces of 1m symmetry is developed and a methodology is described for optimizing the signal-to-noise ratio of extracted hysteresis curves by adjusting the input polarization angle. Quadratic terms in the magnetization are properly accounted for, using recently published formulae. It is shown that, where more than one magnetic region is present, the shape of the extracted hysteresis curve, which contains contributions from the different magnetic regions, varies with the input polarization angle. The new approach is used to determine hysteresis loops from the various magnetic regions of Au-capped ultrathin Fe films grown on a vicinal W(110) substrate. The results for 0.75 ML Fe coverage are of particular interest, revealing distinct contributions from terrace and step Fe atoms. This experimental procedure and phenomenology opens up low symmetry magnetic interfaces and aligned nanostructures to characterization by means of MSHG.
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Affiliation(s)
- L Carroll
- School of Physics, Trinity College Dublin, Dublin 2, Republic of Ireland
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Yokoyama T, Nakagawa T, Takagi Y. Magnetic circular dichroism for surface and thin film magnetism: Measurement techniques and surface chemical applications. INT REV PHYS CHEM 2008. [DOI: 10.1080/01442350802127608] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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21
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Hofer WA, Palotás K, Rusponi S, Cren T, Brune H. Role of hydrogen in giant spin polarization observed on magnetic nanostructures. PHYSICAL REVIEW LETTERS 2008; 100:026806. [PMID: 18232907 DOI: 10.1103/physrevlett.100.026806] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2007] [Indexed: 05/25/2023]
Abstract
We demonstrate that the giant spin contrast observed by scanning tunneling microscopy for double-layer Coislands on Pt(111) is caused by adsorbates at the apex of the Cr-coated W tip. The most likely candidate, in ab initio simulations, is hydrogen. Here, the electron charge is highly polarized by the adjacent Cr layers. The hydrogen adsorption site is shown to change from hollow to on top due to the electric field at the tip apex, created by the tunnel voltage.
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Affiliation(s)
- Werner A Hofer
- Surface Science Research Centre and Department of Physics, University of Liverpool, Liverpool L69 3BX, United Kingdom
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22
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Smogunov A, Dal Corso A, Delin A, Weht R, Tosatti E. Colossal magnetic anisotropy of monatomic free and deposited platinum nanowires. NATURE NANOTECHNOLOGY 2008; 3:22-5. [PMID: 18654445 DOI: 10.1038/nnano.2007.419] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2007] [Accepted: 11/26/2007] [Indexed: 05/05/2023]
Abstract
Whenever a nanosystem such as an adatom, a cluster or a nanowire spontaneously magnetizes, a crucial parameter is its magnetic anisotropy, the intrinsic preference of magnetization to lie along an easy axis. Anisotropy is important in nanosystems because it helps reduce the magnitude of thermal (superparamagnetic) fluctuations, it can modify the flow of current, and it can induce new phenomena, such as the quantum tunnelling of magnetization. We discuss here, on the basis of density functional calculations, the novel and unconventional feature of colossal magnetic anisotropy--the strict impossibility of magnetization to rotate from the parallel to the orthogonal direction--which, owing to a quantum mechanical selection rule, the recently predicted Pt nanowire magnetism should exhibit. Model calculations suggest that the colossal magnetic anisotropy of a Pt chain should persist after weak adsorption on an inert substrate or surface step.
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Bourahla B, Khater A, Tigrine R, Rafil O, Abou Ghantous M. Magnon coherent conductance via atomic nanocontacts. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2007; 19:266208. [PMID: 21694085 DOI: 10.1088/0953-8984/19/26/266208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
A calculation for the coherent scattering and conductance of magnons via atomic nanocontacts is presented. The model system is composed of two groups of semi-infinite magnetically ordered Heisenberg monatomic chains, joined together by the magnetic nanocontact, and the system is supported on a non-magnetic substrate and considered otherwise free from magnetic interactions. The coherent transmission and reflection coefficients are derived as elements of a Landauer-type scattering matrix. Transmission and reflection scattering cross sections are calculated specifically for three distinct symmetric and asymmetric geometric configurations of the nanocontact. Three cases of local magnetic exchange on the nanocontact domain are analysed for each configuration to investigate the influence of softening and hardening of the magnetic boundary conditions. In analogy with coherent electronic transport, we calculate the magnon coherent transport. The numerical results show the interference effects between the incident scattered magnons and the localized spin states on the nanocontact, with characteristic Fano resonances. The numerical results yield an understanding of the relationship between the coherent magnon conductance and the architecture of the embedded magnetic nanocontact.
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Affiliation(s)
- B Bourahla
- Laboratoire de Physique de l'Etat Condensé UMR 6087, Université du Maine, 72085 Le Mans, France. Laboratoire de Physique et Chimie Quantique, Université Mouloud Mammeri, 15000 Tizi-Ouzou, Algeria
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24
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Son YW, Cohen ML, Louie SG. Energy gaps in graphene nanoribbons. PHYSICAL REVIEW LETTERS 2006; 97:216803. [PMID: 17155765 DOI: 10.1103/physrevlett.97.216803] [Citation(s) in RCA: 1447] [Impact Index Per Article: 80.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2006] [Indexed: 05/12/2023]
Abstract
Based on a first-principles approach, we present scaling rules for the band gaps of graphene nanoribbons (GNRs) as a function of their widths. The GNRs considered have either armchair or zigzag shaped edges on both sides with hydrogen passivation. Both varieties of ribbons are shown to have band gaps. This differs from the results of simple tight-binding calculations or solutions of the Dirac's equation based on them. Our ab initio calculations show that the origin of energy gaps for GNRs with armchair shaped edges arises from both quantum confinement and the crucial effect of the edges. For GNRs with zigzag shaped edges, gaps appear because of a staggered sublattice potential on the hexagonal lattice due to edge magnetization. The rich gap structure for ribbons with armchair shaped edges is further obtained analytically including edge effects. These results reproduce our ab initio calculation results very well.
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Affiliation(s)
- Young-Woo Son
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, USA
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25
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Bisio F, Moroni R, Buatier de Mongeot F, Canepa M, Mattera L. Isolating the step contribution to the uniaxial magnetic anisotropy in nanostructured Fe/Ag(001) films. PHYSICAL REVIEW LETTERS 2006; 96:057204. [PMID: 16486975 DOI: 10.1103/physrevlett.96.057204] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2005] [Indexed: 05/06/2023]
Abstract
We have investigated the possibility of isolating the step-induced in-plane uniaxial magnetic anisotropy in Fe/Ag(001) films on which nanoscale surface ripples were fabricated by the ion sculpting technique. For rippled Fe films deposited on flat Ag(001), the steps created along the ripple sidewalls are shown to be the only source of uniaxial anisotropy. Ion sculpting of ultrathin magnetic films allows one to selectively study the step-induced anisotropy and to investigate the correlation between local atomic environment and magnetic properties.
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Affiliation(s)
- F Bisio
- CNR-INFM Unità di Genova and Dipartimento di Fisica, Università di Genova, via Dodecaneso 33, I-16146 Genova, Italy
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26
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Minoda H, Yamamoto N. Study on the origin of the anisotropic dielectric properties of the Au-adsorbed Si(001) vicinal surface. SURF INTERFACE ANAL 2006. [DOI: 10.1002/sia.2439] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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27
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Barth JV, Costantini G, Kern K. Engineering atomic and molecular nanostructures at surfaces. Nature 2005; 437:671-9. [PMID: 16193042 DOI: 10.1038/nature04166] [Citation(s) in RCA: 1164] [Impact Index Per Article: 61.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The fabrication methods of the microelectronics industry have been refined to produce ever smaller devices, but will soon reach their fundamental limits. A promising alternative route to even smaller functional systems with nanometre dimensions is the autonomous ordering and assembly of atoms and molecules on atomically well-defined surfaces. This approach combines ease of fabrication with exquisite control over the shape, composition and mesoscale organization of the surface structures formed. Once the mechanisms controlling the self-ordering phenomena are fully understood, the self-assembly and growth processes can be steered to create a wide range of surface nanostructures from metallic, semiconducting and molecular materials.
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Affiliation(s)
- Johannes V Barth
- Institut de Physique des Nanostructures, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
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28
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Weiss N, Cren T, Epple M, Rusponi S, Baudot G, Rohart S, Tejeda A, Repain V, Rousset S, Ohresser P, Scheurer F, Bencok P, Brune H. Uniform magnetic properties for an ultrahigh-density lattice of noninteracting co nanostructures. PHYSICAL REVIEW LETTERS 2005; 95:157204. [PMID: 16241757 DOI: 10.1103/physrevlett.95.157204] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2005] [Indexed: 05/05/2023]
Abstract
We report on the magnetic properties of two-dimensional Co nanoparticles arranged in macroscopically phase-coherent superlattices created by self-assembly on Au(788). Our particles have a density of 26 Tera/in2 (1 Tera=10(12)), are monodomain, and have uniaxial out-of-plane anisotropy. The distribution of the magnetic anisotropy energies has a half width at half maximum of 17%, a factor of 2 more narrow than the best results reported for superlattices of three-dimensional nanoparticles. Our data show the absence of magnetic interactions between the particles. Co/Au(788) thus constitutes an ideal model system to explore the ultimate density limit of magnetic recording.
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Affiliation(s)
- N Weiss
- Institut de Physique des Nanostructures, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
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29
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Oncel N, van Houselt A, Huijben J, Hallbäck AS, Gurlu O, Zandvliet HJW, Poelsema B. Quantum confinement between self-organized Pt nanowires on Ge(001). PHYSICAL REVIEW LETTERS 2005; 95:116801. [PMID: 16197027 DOI: 10.1103/physrevlett.95.116801] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2005] [Indexed: 05/04/2023]
Abstract
The existence of one-dimensional (1D) electronic states between self-organized Pt nanowires spaced 1.6 or 2.4 nm apart on a Ge(001) surface is revealed by low-temperature scanning tunneling microscopy. These perfectly straight Pt nanowires act as barriers for a surface state (located just below the Fermi level) of the underlying terrace. The energy positions of the 1D electronic states are in good agreement with the energy levels of a quantum particle in a well. Spatial maps of the differential conductivity of the 1D electronic states conclusively reveal that these states are exclusively present in the troughs between the Pt nanowires.
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Affiliation(s)
- Nuri Oncel
- Solid State Physics, MESA+ Research Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
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