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Yoo MW, Tornos J, Sander A, Lin LF, Mohanta N, Peralta A, Sanchez-Manzano D, Gallego F, Haskel D, Freeland JW, Keavney DJ, Choi Y, Strempfer J, Wang X, Cabero M, Vasili HB, Valvidares M, Sanchez-Santolino G, Gonzalez-Calbet JM, Rivera A, Leon C, Rosenkranz S, Bibes M, Barthelemy A, Anane A, Dagotto E, Okamoto S, te Velthuis SGE, Santamaria J, Villegas JE. Large intrinsic anomalous Hall effect in SrIrO 3 induced by magnetic proximity effect. Nat Commun 2021; 12:3283. [PMID: 34078889 PMCID: PMC8172877 DOI: 10.1038/s41467-021-23489-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Accepted: 04/25/2021] [Indexed: 02/04/2023] Open
Abstract
The anomalous Hall effect (AHE) is an intriguing transport phenomenon occurring typically in ferromagnets as a consequence of broken time reversal symmetry and spin-orbit interaction. It can be caused by two microscopically distinct mechanisms, namely, by skew or side-jump scattering due to chiral features of the disorder scattering, or by an intrinsic contribution directly linked to the topological properties of the Bloch states. Here we show that the AHE can be artificially engineered in materials in which it is originally absent by combining the effects of symmetry breaking, spin orbit interaction and proximity-induced magnetism. In particular, we find a strikingly large AHE that emerges at the interface between a ferromagnetic manganite (La0.7Sr0.3MnO3) and a semimetallic iridate (SrIrO3). It is intrinsic and originates in the proximity-induced magnetism present in the narrow bands of strong spin-orbit coupling material SrIrO3, which yields values of anomalous Hall conductivity and Hall angle as high as those observed in bulk transition-metal ferromagnets. These results demonstrate the interplay between correlated electron physics and topological phenomena at interfaces between 3d ferromagnets and strong spin-orbit coupling 5d oxides and trace an exciting path towards future topological spintronics at oxide interfaces.
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Affiliation(s)
- Myoung-Woo Yoo
- grid.460789.40000 0004 4910 6535Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, Palaiseau, France
| | - J. Tornos
- grid.4795.f0000 0001 2157 7667GFMC, Dept. Fisica de Materiales, Facultad de Fisica, Universidad Complutense, Madrid, Spain
| | - A. Sander
- grid.460789.40000 0004 4910 6535Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, Palaiseau, France
| | - Ling-Fang Lin
- grid.411461.70000 0001 2315 1184Department of Physics and Astronomy, University of Tennessee, Knoxville, TN USA ,grid.263826.b0000 0004 1761 0489School of Physics, Southeast University, Nanjing, China
| | - Narayan Mohanta
- grid.135519.a0000 0004 0446 2659Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
| | - A. Peralta
- grid.4795.f0000 0001 2157 7667GFMC, Dept. Fisica de Materiales, Facultad de Fisica, Universidad Complutense, Madrid, Spain
| | - D. Sanchez-Manzano
- grid.4795.f0000 0001 2157 7667GFMC, Dept. Fisica de Materiales, Facultad de Fisica, Universidad Complutense, Madrid, Spain
| | - F. Gallego
- grid.4795.f0000 0001 2157 7667GFMC, Dept. Fisica de Materiales, Facultad de Fisica, Universidad Complutense, Madrid, Spain
| | - D. Haskel
- grid.187073.a0000 0001 1939 4845Advanced Photon Source Argonne National Laboratory, Lemont, IL USA
| | - J. W. Freeland
- grid.187073.a0000 0001 1939 4845Advanced Photon Source Argonne National Laboratory, Lemont, IL USA
| | - D. J. Keavney
- grid.187073.a0000 0001 1939 4845Advanced Photon Source Argonne National Laboratory, Lemont, IL USA
| | - Y. Choi
- grid.187073.a0000 0001 1939 4845Advanced Photon Source Argonne National Laboratory, Lemont, IL USA
| | - J. Strempfer
- grid.187073.a0000 0001 1939 4845Advanced Photon Source Argonne National Laboratory, Lemont, IL USA
| | - X. Wang
- grid.253355.70000 0001 2192 5641Department of Physics, Bryn Mawr College, Bryn Mawr, PA USA
| | - M. Cabero
- grid.5515.40000000119578126IMDEA Nanoscience Campus Universidad Autonoma, Cantoblanco, Spain ,grid.4795.f0000 0001 2157 7667Centro Nacional de Microscopia Electronica, Universidad Complutense, Madrid, Spain
| | - Hari Babu Vasili
- grid.423639.9CELLS-ALBA Synchrotron Radiation Facility, Cerdanyola del Valles, Spain
| | - Manuel Valvidares
- grid.423639.9CELLS-ALBA Synchrotron Radiation Facility, Cerdanyola del Valles, Spain
| | - G. Sanchez-Santolino
- grid.4795.f0000 0001 2157 7667GFMC, Dept. Fisica de Materiales, Facultad de Fisica, Universidad Complutense, Madrid, Spain
| | - J. M. Gonzalez-Calbet
- grid.4795.f0000 0001 2157 7667Centro Nacional de Microscopia Electronica, Universidad Complutense, Madrid, Spain ,grid.4795.f0000 0001 2157 7667Department Quimica Inorganica, Facultad de Quimica, Universidad Complutense, Madrid, Spain
| | - A. Rivera
- grid.4795.f0000 0001 2157 7667GFMC, Dept. Fisica de Materiales, Facultad de Fisica, Universidad Complutense, Madrid, Spain
| | - C. Leon
- grid.4795.f0000 0001 2157 7667GFMC, Dept. Fisica de Materiales, Facultad de Fisica, Universidad Complutense, Madrid, Spain
| | - S. Rosenkranz
- grid.187073.a0000 0001 1939 4845Materials Science Division, Argonne National Laboratory, Lemont, IL USA
| | - M. Bibes
- grid.460789.40000 0004 4910 6535Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, Palaiseau, France
| | - A. Barthelemy
- grid.460789.40000 0004 4910 6535Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, Palaiseau, France
| | - A. Anane
- grid.460789.40000 0004 4910 6535Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, Palaiseau, France
| | - Elbio Dagotto
- grid.411461.70000 0001 2315 1184Department of Physics and Astronomy, University of Tennessee, Knoxville, TN USA ,grid.135519.a0000 0004 0446 2659Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
| | - S. Okamoto
- grid.135519.a0000 0004 0446 2659Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
| | - S. G. E. te Velthuis
- grid.187073.a0000 0001 1939 4845Materials Science Division, Argonne National Laboratory, Lemont, IL USA
| | - J. Santamaria
- grid.4795.f0000 0001 2157 7667GFMC, Dept. Fisica de Materiales, Facultad de Fisica, Universidad Complutense, Madrid, Spain
| | - Javier E. Villegas
- grid.460789.40000 0004 4910 6535Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, Palaiseau, France
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2
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Sung D, Jung C, Cho BG, Jo W, Han HS, Lee KS, Bhat V, Farmer B, De Long LE, Lee KB, Keavney DJ, Lee DR, Song C. Imaging the magnetic structures of artificial quasicrystal magnets using resonant coherent diffraction of circularly polarized X-rays. Nanoscale 2018; 10:13159-13164. [PMID: 29963676 DOI: 10.1039/c8nr03733g] [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: 06/08/2023]
Abstract
Unraveling nanoscale spin structures has long been an important activity addressing various scientific interests, that are also readily adaptable to technological applications. This has invigorated the development of versatile nanoprobes suitable for imaging specimens under native conditions. Here we have demonstrated the resonant coherent diffraction of an artificial quasicrystal magnet with circularly polarized X-rays. The nanoscale magnetic structure was revealed from X-ray speckle patterns by comparing with micromagnetic simulations, as a step toward understanding the intricate relationship between the chemical and spin structures in an aperiodic quasicrystal lattice. Femtosecond X-ray pulses from free electron lasers are expected to immediately extend the current work to nanoscale structure investigations of ultrafast spin dynamics, surpassing the present spatio-temporal resolution.
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Affiliation(s)
- Daeho Sung
- Department of Physics, POSTECH, Pohang 37673, Korea.
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3
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Farmer B, Bhat VS, Balk A, Teipel E, Smith N, Unguris J, Keavney DJ, Hastings JT, De Long LE. Direct imaging of coexisting ordered and frustrated sublattices in artificial ferromagnetic quasicrystals. Phys Rev B 2016; 93:134428. [PMID: 28691109 PMCID: PMC5497597 DOI: 10.1103/physrevb.93.134428] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [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 have used scanning electron microscopy with polarization analysis and photoemission electron microscopy to image the two-dimensional magnetization of permalloy films patterned into Penrose P2 tilings (P2T). The interplay of exchange interactions in asymmetrically coordinated vertices and short-range dipole interactions among connected film segments stabilize magnetically ordered, spatially distinct sublattices that coexist with frustrated sublattices at room temperature. Numerical simulations that include long-range dipole interactions between sublattices agree with images of as-grown P2T samples and predict a magnetically ordered ground state for a two-dimensional quasicrystal lattice of classical Ising spins.
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Affiliation(s)
- B Farmer
- Department of Physics and Astronomy, University of Kentucky, 505 Rose Street, Lexington, Kentucky 40506-0055, USA
| | - V S Bhat
- Department of Physics and Astronomy, University of Kentucky, 505 Rose Street, Lexington, Kentucky 40506-0055, USA
| | - A Balk
- Center for Nanoscale Science and Technology, National Institute of Standards and Technology, 100 Bureau Dr., Gaithersburg, Maryland 20899, USA
- Maryland Nanocenter, University of Maryland, College Park, Maryland 20742, USA
| | - E Teipel
- Department of Physics and Astronomy, University of Kentucky, 505 Rose Street, Lexington, Kentucky 40506-0055, USA
| | - N Smith
- Department of Physics and Astronomy, University of Kentucky, 505 Rose Street, Lexington, Kentucky 40506-0055, USA
| | - J Unguris
- Center for Nanoscale Science and Technology, National Institute of Standards and Technology, 100 Bureau Dr., Gaithersburg, Maryland 20899, USA
| | - D J Keavney
- Advanced Photon Source 431-E007, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, Illinois 60439, USA
| | - J T Hastings
- Department of Electrical and Computer Engineering, University of Kentucky, 453F Paul Anderson Tower, Lexington, Kentucky 40506-0046, USA
| | - L E De Long
- Department of Physics and Astronomy, University of Kentucky, 505 Rose Street, Lexington, Kentucky 40506-0055, USA
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4
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Estrader M, López-Ortega A, Estradé S, Golosovsky IV, Salazar-Alvarez G, Vasilakaki M, Trohidou KN, Varela M, Stanley DC, Sinko M, Pechan MJ, Keavney DJ, Peiró F, Suriñach S, Baró MD, Nogués J. Robust antiferromagnetic coupling in hard-soft bi-magnetic core/shell nanoparticles. Nat Commun 2014; 4:2960. [PMID: 24343382 DOI: 10.1038/ncomms3960] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Accepted: 11/19/2013] [Indexed: 11/10/2022] Open
Abstract
The growing miniaturization demand of magnetic devices is fuelling the recent interest in bi-magnetic nanoparticles as ultimate small components. One of the main goals has been to reproduce practical magnetic properties observed so far in layered systems. In this context, although useful effects such as exchange bias or spring magnets have been demonstrated in core/shell nanoparticles, other interesting key properties for devices remain elusive. Here we show a robust antiferromagnetic (AFM) coupling in core/shell nanoparticles which, in turn, leads to the foremost elucidation of positive exchange bias in bi-magnetic hard-soft systems and the remarkable regulation of the resonance field and amplitude. The AFM coupling in iron oxide-manganese oxide based, soft/hard and hard/soft, core/shell nanoparticles is demonstrated by magnetometry, ferromagnetic resonance and X-ray magnetic circular dichroism. Monte Carlo simulations prove the consistency of the AFM coupling. This unique coupling could give rise to more advanced applications of bi-magnetic core/shell nanoparticles.
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Affiliation(s)
- M Estrader
- 1] ICN2-Institut Catala de Nanociencia i Nanotecnologia, Campus UAB, E-08193 Bellaterra, Barcelona, Spain [2] Departament de Química Inorgànica, Universitat de Barcelona, Diagonal 645, E-08028 Barcelona, Spain
| | - A López-Ortega
- 1] ICN2-Institut Catala de Nanociencia i Nanotecnologia, Campus UAB, E-08193 Bellaterra, Barcelona, Spain [2] INSTM and Dipartimento di Chimica 'U. Schiff', Università degli Studi di Firenze, Via della Lastruccia 3, Sesto Fiorentino, I-50019 Firenze, Italy
| | - S Estradé
- 1] LENS-MIND-IN2UB, Departament d'Electrònica, Universitat de Barcelona, Martí i Franquès 1, E-08028 Barcelona, Spain [2] TEM-MAT, SCT, Universitat de Barcelona, E-08028 Barcelona, Spain
| | - I V Golosovsky
- 1] St Petersburg Nuclear Physics Institute, 188300 Gatchina, St Petersburg, Russia [2] Ioffe Physico-Technical Institute of the RAS, 194021 St Petersburg, Russia
| | - G Salazar-Alvarez
- Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, 10691 Stockholm, Sweden
| | - M Vasilakaki
- IAMPPMN, Department of Materials Science, NCSR 'Demokritos', 153 41 Aghia Paraskevi, Attiki, Greece
| | - K N Trohidou
- IAMPPMN, Department of Materials Science, NCSR 'Demokritos', 153 41 Aghia Paraskevi, Attiki, Greece
| | - M Varela
- 1] Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA [2] Departamento de Física Aplicada III & Instituto Pluridisciplinar, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - D C Stanley
- Department of Physics, Miami University, Oxford, Ohio 45056, USA
| | - M Sinko
- Department of Physics, Miami University, Oxford, Ohio 45056, USA
| | - M J Pechan
- Department of Physics, Miami University, Oxford, Ohio 45056, USA
| | - D J Keavney
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - F Peiró
- LENS-MIND-IN2UB, Departament d'Electrònica, Universitat de Barcelona, Martí i Franquès 1, E-08028 Barcelona, Spain
| | - S Suriñach
- Departament de Física, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Barcelona, Spain
| | - M D Baró
- Departament de Física, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Barcelona, Spain
| | - J Nogués
- 1] ICN2-Institut Catala de Nanociencia i Nanotecnologia, Campus UAB, E-08193 Bellaterra, Barcelona, Spain [2] Departament de Física, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Barcelona, Spain [3] Institució Catalana de Recerca i Estudis Avançats (ICREA), E-08010 Barcelona, Spain
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5
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Moon EJ, Balachandran PV, Kirby BJ, Keavney DJ, Sichel-Tissot RJ, Schlepütz CM, Karapetrova E, Cheng XM, Rondinelli JM, May SJ. Effect of interfacial octahedral behavior in ultrathin manganite films. Nano Lett 2014; 14:2509-14. [PMID: 24697503 DOI: 10.1021/nl500235f] [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] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We investigate structural coupling of the MnO6 octahedra across a film/substrate interface and the resultant changes of the physical properties of ultrathin La2/3Sr1/3MnO3 (LSMO) films. In order to isolate the effect of interfacial MnO6 octahedral behavior from that of epitaxial strain, LSMO films are grown on substrates with different symmetry and similar lattice parameters. Ultrathin LSMO films show an increased magnetization and electrical conductivity on cubic (LaAlO3)0.3(Sr2AlTaO6)0.7 (LSAT) compared to those grown on orthorhombic NdGaO3 (NGO) substrates, an effect that subsides as the thickness of the films is increased. This study demonstrates that interfacial structural coupling can play a critical role in the functional properties of oxide heterostructures.
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Affiliation(s)
- E J Moon
- Department of Materials Science and Engineering, Drexel University , Philadelphia, Pennsylvania 19104, United States
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6
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Reininger R, Keavney DJ, Borland M, Young L. Optical design of the Short Pulse Soft X-ray Spectroscopy beamline at the Advanced Photon Source. J Synchrotron Radiat 2013; 20:654-9. [PMID: 23765311 PMCID: PMC3943553 DOI: 10.1107/s0909049513013149] [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] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Accepted: 05/13/2013] [Indexed: 05/16/2023]
Abstract
The Short Pulse X-ray facility planned for the Advanced Photon Source (APS) upgrade will provide two sectors with photon beams having picosecond pulse duration. The Short Pulse Soft X-ray Spectroscopy (SPSXS) beamline will cover the 150-2000 eV energy range using an APS bending magnet. SPSXS is designed to take full advantage of this new timing capability in addition to providing circular polarized radiation. Since the correlation between time and electron momentum is in the vertical plane, the monochromator disperses in the horizontal plane. The beamline is designed to maximize flux and preserve the time resolution by minimizing the number of optical components. The optical design allows the pulse duration to be varied from 1.5 to 100 ps full width at half-maximum (FWHM) without affecting the energy resolution, and the resolution to be changed with minimal effect on the pulse duration. More than 10(9) photons s(-1) will reach the sample with a resolving power of 2000 and a pulse duration of ∼2 ps for photon energies between 150 and 1750 eV. The spot size expected at the sample position will vary with pulse duration and exit slit opening. At 900 eV and at a resolving power of 2000 the spot will be ∼10 µm × 10 µm with a pulse duration of 2.3 ps FWHM.
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Affiliation(s)
- R Reininger
- Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA.
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7
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López-Ortega A, Estrader M, Salazar-Alvarez G, Estradé S, Golosovsky IV, Dumas RK, Keavney DJ, Vasilakaki M, Trohidou KN, Sort J, Peiró F, Suriñach S, Baró MD, Nogués J. Strongly exchange coupled inverse ferrimagnetic soft/hard, Mn(x)Fe(3-x)O4/Fe(x)Mn(3-x)O4, core/shell heterostructured nanoparticles. Nanoscale 2012; 4:5138-47. [PMID: 22797330 DOI: 10.1039/c2nr30986f] [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: 05/12/2023]
Abstract
Inverted soft/hard, in contrast to conventional hard/soft, bi-magnetic core/shell nanoparticles of Mn(x)Fe(3-x)O(4)/Fe(x)Mn(3-x)O(4) with two different core sizes (7.5 and 11.5 nm) and fixed shell thickness (∼0.6 nm) have been synthesized. The structural characterization suggests that the particles have an interface with a graded composition. The magnetic characterization confirms the inverted soft/hard structure and evidences a strong exchange coupling between the core and the shell. Moreover, larger soft core sizes exhibit smaller coercivities and loop shifts, but larger blocking temperatures, as expected from spring-magnet or graded anisotropy structures. The results indicate that, similar to thin film systems, the magnetic properties of soft/hard core/shell nanoparticles can be fine tuned to match specific applications.
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Affiliation(s)
- A López-Ortega
- CIN2(ICN-CSIC) and Universitat Autònoma de Barcelona, Catalan Institute of Nanotechnology, Campus de la UAB, 08193 Bellaterra (Barcelona), Spain
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8
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de Groot J, Mueller T, Rosenberg RA, Keavney DJ, Islam Z, Kim JW, Angst M. Charge order in LuFe2O4: an unlikely route to ferroelectricity. Phys Rev Lett 2012; 108:187601. [PMID: 22681119 DOI: 10.1103/physrevlett.108.187601] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Indexed: 06/01/2023]
Abstract
We present the refinement of the crystal structure of charge-ordered LuFe2O4, based on single-crystal x-ray diffraction data. The arrangement of the different Fe-valence states, determined with bond-valence-sum analysis, corresponds to a stacking of charged Fe bilayers, in contrast with the polar bilayers previously suggested. This arrangement is supported by an analysis of x-ray magnetic circular dichroism spectra, which also evidences a strong charge-spin coupling. The nonpolar bilayers are inconsistent with charge order based ferroelectricity.
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Affiliation(s)
- J de Groot
- Peter Grünberg Institut PGI and Jülich Centre for Neutron Science JCNS, JARA-FIT, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
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9
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Abstract
As interest in magnetic devices has increased over the last 20 years, research into nanomagnetism has experienced a corresponding growth. Device applications from magnetic storage to magnetic logic have compelled interest in the influence of geometry and finite size on magnetism and magnetic excitations, in particular where the smallest dimensions reach the important magnetic interaction length scales. The dynamical behavior of nanoscale magnets is an especially important subset of research, as these phenomena are both critical for device physics and profoundly influenced by finite size. At the same time, nanoscale systems offer unique geometries to promote and study model systems, such as magnetic vortices, leading to new fundamental insights into magnetization dynamics. A wide array of experimental and computational techniques have been applied to these problems. Among these, imaging techniques that provide real-space information on the magnetic order are particularly useful. X-ray microscopy offers several advantages over scanning probe or optical techniques, such as high spatial resolution, element specificity and the possibility for high time resolution. Here, we review recent contributions using static and time-resolved x-ray photoemission electron microscopy to nanomagnetism research.
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Affiliation(s)
- X M Cheng
- Department of Physics, Bryn Mawr College, Bryn Mawr, PA, USA
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10
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Han XF, Grimsditch M, Meersschaut J, Hoffmann A, Ji Y, Sort J, Nogués J, Divan R, Pearson JE, Keavney DJ. Magnetic instability regions in patterned structures: influence of element shape on magnetization reversal dynamics. Phys Rev Lett 2007; 98:147202. [PMID: 17501307 DOI: 10.1103/physrevlett.98.147202] [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: 08/15/2006] [Indexed: 05/15/2023]
Abstract
We report a time-resolved imaging study of the influence of shape on magnetic instabilities in patterned magnetic structures. We find that in rectangular structures magnetization reversal initiates at the ends and interior simultaneously, while in structures with tapered ends the reversal begins in the middle of the structures and spreads out to the ends. The degree of tapering is important for both the switching field and the time required for full reversal. A model based on the concept of local instability regions yields good agreement with the observed location of the reversal onsets.
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Affiliation(s)
- X F Han
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
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11
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Krishnamurthy VV, Lang JC, Haskel D, Keavney DJ, Srajer G, Robertson JL, Sales BC, Mandrus DG, Singh DJ, Bilc DI. Ferrimagnetism in EuFe4Sb12 due to the interplay of f-electron moments and a nearly ferromagnetic host. Phys Rev Lett 2007; 98:126403. [PMID: 17501140 DOI: 10.1103/physrevlett.98.126403] [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] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2006] [Indexed: 05/15/2023]
Abstract
We combine x-ray magnetic circular dichroism spectroscopy at Fe L2,3 edges, at Eu M4,5 edges, x-ray absorption spectroscopy (XAS) investigation of Eu valence, and local spin density calculations, to show that the filled skutterudite Eu0.95Fe4Sb12 is a ferrimagnet in which the Fe 3d moment and the Eu2+ 4f moment are magnetically ordered with dominant antiferromagnetic coupling. From Eu L3 edge XAS, we find that about 13% of the Eu have a formal valence of 3+. We ascribe the origin of ferrimagnetism at a relatively high transition temperature TC of 85 K in Eu0.95Fe4Sb12 to f-electron interaction with the nearly ferromagnetic [Fe4Sb12]2.2- host lattice.
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Affiliation(s)
- V V Krishnamurthy
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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12
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Guslienko KY, Han XF, Keavney DJ, Divan R, Bader SD. Magnetic vortex core dynamics in cylindrical ferromagnetic dots. Phys Rev Lett 2006; 96:067205. [PMID: 16606041 DOI: 10.1103/physrevlett.96.067205] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2005] [Indexed: 05/08/2023]
Abstract
We report direct imaging by means of x-ray photoemission electron microscopy of the dynamics of magnetic vortices confined in micron-sized circular permalloy dots that are 30 nm thick. The vortex core positions oscillate on a 10 ns time scale in a self-induced magnetostatic potential well after the in-plane magnetic field is turned off. The measured oscillation frequencies as a function of the aspect ratio of the dots are in agreement with theoretical calculations presented for the same geometry.
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Affiliation(s)
- K Yu Guslienko
- Materials Science Division and Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.
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13
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Keavney DJ, Cheung SH, King ST, Weinert M, Li L. Role of defect sites and Ga polarization in the magnetism of Mn-doped GaN. Phys Rev Lett 2005; 95:257201. [PMID: 16384500 DOI: 10.1103/physrevlett.95.257201] [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] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2005] [Indexed: 05/05/2023]
Abstract
We report a study of the Mn local structure, magnetism, and Ga moments in molecular beam epitaxy grown Mn-doped GaN films. Using x-ray absorption spectroscopy and magnetic circular dichroism, we find two distinct Mn sites and a Ga moment antiparallel to Mn. First-principles calculations reproduce this phenomenology and indicate that Mn preferentially populates Ga sites neighboring N split interstitial defects. These results show that defects may strongly affect the Mn ordering and magnetism, and that the GaN valence band is polarized, providing a long-range ferromagnetic ordering mechanism for Ga1-xMnxN.
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Affiliation(s)
- D J Keavney
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
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Keavney DJ, Wu D, Freeland JW, Johnston-Halperin E, Awschalom DD, Shi J. Element resolved spin configuration in ferromagnetic manganese-doped gallium arsenide. Phys Rev Lett 2003; 91:187203. [PMID: 14611312 DOI: 10.1103/physrevlett.91.187203] [Citation(s) in RCA: 8] [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: 07/02/2003] [Indexed: 05/24/2023]
Abstract
We report induced Ga and As moments in ferromagnetic Ga(1-x)MnxAs detected using x-ray magnetic circular dichroism at the Mn, Ga, and As L(3,2) edges. Across a broad composition range, we find As and Ga dichroism signals which indicate an As 4s moment coupled antiparallel to the Mn 3d moment, and a smaller parallel Ga 4s moment. The Ga moment follows that of Mn in both doping and temperature dependence. These results are consistent with recent predictions of induced GaAs host moments and support the model of carrier-mediated ferromagnetic ordering involving As-derived valence band states.
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Affiliation(s)
- D J Keavney
- Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA
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Freeland JW, Keavney DJ, Storm DF, Grigorov IL, Walker JC, Pini MG, Politi P, Rettori A. Oscillatory ferromagnetic interlayer coupling of Fe(110) thin films through (111) oriented Ag and Cu spacers. Phys Rev B Condens Matter 1996; 54:9942-9951. [PMID: 9984730 DOI: 10.1103/physrevb.54.9942] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Keavney DJ, Storm DF, Freeland JW, Grigorov IL, Walker JC. Site-specific Mössbauer evidence of structure-induced magnetic phase transition in fcc Fe(100) thin films. Phys Rev Lett 1995; 74:4531-4534. [PMID: 10058530 DOI: 10.1103/physrevlett.74.4531] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Keavney DJ, Storm DF, Freeland JW, Wieczorek MD, Walker JC, Pini MG, Politi P, Rettori A. Oscillatory exchange coupling of ferromagnetically aligned Fe(110) layers through Ag(111) interlayers. Phys Rev Lett 1993; 71:927-930. [PMID: 10055403 DOI: 10.1103/physrevlett.71.927] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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