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Okabayashi J, Miura Y, Kota Y, Z Suzuki K, Sakuma A, Mizukami S. Detecting quadrupole: a hidden source of magnetic anisotropy for Manganese alloys. Sci Rep 2020; 10:9744. [PMID: 32546779 PMCID: PMC7297735 DOI: 10.1038/s41598-020-66432-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Accepted: 05/07/2020] [Indexed: 11/25/2022] Open
Abstract
Mn-based alloys exhibit unique properties in the spintronics materials possessing perpendicular magnetic anisotropy (PMA) beyond the Fe and Co-based alloys. It is desired to figure out the quantum physics of PMA inherent to Mn-based alloys, which have never been reported. Here, the origin of PMA in ferrimagnetic Mn3− δ Ga ordered alloys is investigated to resolve antiparallel-coupled Mn sites using x-ray magnetic circular and linear dichroism (XMCD/XMLD) and a first-principles calculation. We found that the contribution of orbital magnetic moments in PMA is small from XMCD and that the finite quadrupole-like orbital distortion through spin-flipped electron hopping is dominant from XMLD and theoretical calculations. These findings suggest that the spin-flipped orbital quadrupole formations originate from the PMA in Mn3− δ Ga and bring the paradigm shift in the researches of PMA materials using x-ray magnetic spectroscopies.
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Affiliation(s)
- Jun Okabayashi
- Research Center for Spectrochemistry, The University of Tokyo, 113-0033, Tokyo, Japan.
| | - Yoshio Miura
- Research Center for Magnetic and Spintronic Materials, National Institute for Materials Science (NIMS), Tsukuba, 305-0047, Japan
| | - Yohei Kota
- National Institute of Technology, Fukushima College, Iwaki, Fukushima, 970-8034, Japan
| | - Kazuya Z Suzuki
- WPI-Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,Center for Spintronics Research Network (CSRN), Tohoku University, Sendai, 980-8579, Japan
| | - Akimasa Sakuma
- Center for Spintronics Research Network (CSRN), Tohoku University, Sendai, 980-8579, Japan.,Department of Applied Physics, Tohoku University, Sendai, 980-8579, Japan.,Center for Science and Innovation in Spintronics (CSIS), Tohoku University, Sendai, 980-8577, Japan
| | - Shigemi Mizukami
- WPI-Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,Center for Spintronics Research Network (CSRN), Tohoku University, Sendai, 980-8579, Japan.,Center for Science and Innovation in Spintronics (CSIS), Tohoku University, Sendai, 980-8577, Japan
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2
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Liu WC, Chiu YH, Kung YY, Liao PY, Cheng CH, Chih YC, Tsai YW, Chu CH, Lai CH, Huang DJ, Soo YL, Chang SL. Revisiting La 0.5Sr 1.5MnO 4 lattice distortion and charge ordering with multi-beam resonant diffraction. ACTA CRYSTALLOGRAPHICA A-FOUNDATION AND ADVANCES 2017; 73:46-53. [PMID: 28042803 DOI: 10.1107/s2053273316013759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 08/27/2016] [Indexed: 11/11/2022]
Abstract
Sinusoidal wave type distortions of La0.5Sr1.5MnO4 in the low-temperature orthorhombic phase were observed using multi-beam resonant X-ray diffraction (MRXD) with (7/4 7/4 0) fractional primary diffraction. Two four-beam diffractions with opposite asymmetry were measured at 6.5545 keV and compared with the curves simulated by the dynamical X-ray diffraction theory. This approach provides the possibility of resolving the distortion modes which are perpendicular to the momentum transfer by a single azimuthal scan. The paper also demonstrates the sensitivity of MRXD profiles versus incident X-ray energy in the vicinity of the Mn K edge to the charge disproportion between the two manganese sites, reconfirming the small charge disproportion feature.
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Affiliation(s)
- Wen Chung Liu
- Department of Physics, Tsing Hua University, Hsinchu, 30013, Taiwan
| | - Yi Hua Chiu
- Department of Physics, Tsing Hua University, Hsinchu, 30013, Taiwan
| | - Ying Yu Kung
- Department of Physics, Tsing Hua University, Hsinchu, 30013, Taiwan
| | - Po Yu Liao
- Department of Physics, Tsing Hua University, Hsinchu, 30013, Taiwan
| | - Chih Hao Cheng
- Department of Physics, Tsing Hua University, Hsinchu, 30013, Taiwan
| | - Yu Chieh Chih
- Department of Physics, Tsing Hua University, Hsinchu, 30013, Taiwan
| | - Yi Wei Tsai
- Department of Physics, Tsing Hua University, Hsinchu, 30013, Taiwan
| | - Chia Hung Chu
- National Synchrotron Radiation Research Center, Hsinchu, 30076, Taiwan
| | - Chia Hung Lai
- Department of Physics, Tsing Hua University, Hsinchu, 30013, Taiwan
| | - Di Jing Huang
- National Synchrotron Radiation Research Center, Hsinchu, 30076, Taiwan
| | - Yun Liang Soo
- Department of Physics, Tsing Hua University, Hsinchu, 30013, Taiwan
| | - Shih Lin Chang
- Department of Physics, Tsing Hua University, Hsinchu, 30013, Taiwan
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3
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Haw SC, Lee JM, Chen SA, Lu KT, Lee MT, Pi TW, Lee CH, Hu Z, Chen JM. Influence of Fe substitution on the Jahn-Teller distortion and orbital anisotropy in orthorhombic Y(Mn1-xFex)O3 epitaxial films. Dalton Trans 2016; 45:12393-9. [PMID: 27430045 DOI: 10.1039/c6dt01633b] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Multiferroic YMn1-xFexO3(020) (x = 0.125, 0.25, 0.50) epitaxial thin films with an orthorhombic structure (space group Pbnm) were prepared on a YAlO3(010) substrate by pulsed-laser deposition. Upon Fe substitution, the b-axis was clearly shortened, whereas the a- and c-axes were slightly lengthened based on XRD analysis. To understand the influence of orbital polarization and the Jahn-Teller effect of Mn(3+) on Fe substitution and also the local octahedral-site distortion of Fe(3+) in an environment of Jahn-Teller-active Mn(3+) ions in YMn1-xFexO3 films, we measured the polarization-dependent X-ray absorption spectra at the Mn-L2,3 and Fe-L2,3 edges, and also simulated the experimental spectra using configuration-interaction multiplet calculations. Although Δeg for the Mn(3+) ion decreased from 0.9 eV in pure YMnO3 to 0.6 eV in the half-Fe-substituted sample, a single eg electron was still strongly constrained to the d3y(2)-r(2) orbital for all the Fe concentrations tested. The largest Δeg, 0.5 eV, for the Fe(3+) ion was derived for a sample with 12.5% Fe substitution, and gradually decreased to 0.15 eV for the half-Fe-substituted sample. The local octahedral-site distortion of the Fe(3+) ion inside the YMnO3 lattice was similar to that of the Mn(3+) ion, whereas the Jahn-Teller distortion and GdFeO3-type distortion of the Mn(3+) ion were decreased by the spherical high-spin Fe(3+) ions. The combination of the experimental and theoretical data provides both profound insight into the variation of the Jahn-Teller distortion and orbital anisotropy and instructive information about the magnetic structures in these orthorhombic YMn1-xFexO3 thin films.
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Affiliation(s)
- Shu-Chih Haw
- National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, 30076 Hsinchu, Taiwan.
| | - Jenn-Min Lee
- National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, 30076 Hsinchu, Taiwan.
| | - Shin-Ann Chen
- National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, 30076 Hsinchu, Taiwan.
| | - Kueih-Tzu Lu
- National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, 30076 Hsinchu, Taiwan.
| | - Ming-Tao Lee
- National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, 30076 Hsinchu, Taiwan.
| | - Tun-Wen Pi
- National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, 30076 Hsinchu, Taiwan.
| | - Chih-Hao Lee
- Department of Engineering and System Science, National Tsing Hua University, 30013 Hsinchu, Taiwan
| | - Zhiwei Hu
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - Jin-Ming Chen
- National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, 30076 Hsinchu, Taiwan.
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4
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Middey S, Meyers D, Doennig D, Kareev M, Liu X, Cao Y, Yang Z, Shi J, Gu L, Ryan PJ, Pentcheva R, Freeland JW, Chakhalian J. Mott Electrons in an Artificial Graphenelike Crystal of Rare-Earth Nickelate. PHYSICAL REVIEW LETTERS 2016; 116:056801. [PMID: 26894726 DOI: 10.1103/physrevlett.116.056801] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2015] [Indexed: 06/05/2023]
Abstract
Deterministic control over the periodic geometrical arrangement of the constituent atoms is the backbone of the material properties, which, along with the interactions, define the electronic and magnetic ground state. Following this notion, a bilayer of a prototypical rare-earth nickelate, NdNiO_{3}, combined with a dielectric spacer, LaAlO_{3}, has been layered along the pseudocubic [111] direction. The resulting artificial graphenelike Mott crystal with magnetic 3d electrons has antiferromagnetic correlations. In addition, a combination of resonant X-ray linear dichroism measurements and ab initio calculations reveal the presence of an ordered orbital pattern, which is unattainable in either bulk nickelates or nickelate based heterostructures grown along the [001] direction. These findings highlight another promising venue towards designing new quantum many-body states by virtue of geometrical engineering.
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Affiliation(s)
- S Middey
- Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, USA
| | - D Meyers
- Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, USA
| | - D Doennig
- Department of Earth and Environmental Sciences and Center of Nanoscience, University of Munich, Munich D-80333, Germany
| | - M Kareev
- Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, USA
| | - X Liu
- Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, USA
| | - Y Cao
- Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, USA
| | - Zhenzhong Yang
- Beijing National Laboratory for Condensed-Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Jinan Shi
- Beijing National Laboratory for Condensed-Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Lin Gu
- Beijing National Laboratory for Condensed-Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- Collaborative Innovation Center of Quantum Matter, Beijing 100190, People's Republic of China
| | - P J Ryan
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - R Pentcheva
- Department of Earth and Environmental Sciences and Center of Nanoscience, University of Munich, Munich D-80333, Germany
- Department of Physics, University of Duisburg-Essen, Duisburg D-47057, Germany
| | - J W Freeland
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - J Chakhalian
- Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, USA
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5
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Valencia S, Peña L, Konstantinovic Z, Balcells L, Galceran R, Schmitz D, Sandiumenge F, Casanove M, Martínez B. Intrinsic antiferromagnetic/insulating phase at manganite surfaces and interfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:166001. [PMID: 24691398 DOI: 10.1088/0953-8984/26/16/166001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
In this work we investigate interfacial effects in bilayer systems integrated by La(2/3)Sr(1/3)MnO(3) (LSMO) thin films and different capping layers by means of surface-sensitive synchrotron radiation techniques and transport measurements. Our data reveal a complex scenario with a capping-dependent variation of the Mn oxidation state by the interface. However, irrespective of the capping material, an antiferromagnetic/insulating phase is also detected at the interface, which is likely to originate from a preferential occupancy of Mn 3d 3z(2)-r(2) e(g) orbitals. This phase, which extends approximately to two unit cells, is also observed in uncapped LSMO reference samples, thus pointing to an intrinsic interfacial phase separation phenomenon, probably promoted by the structural disruption and inversion symmetry breaking at the LSMO free surface/interface. These experimental observations strongly suggest that the structural disruption, with its intrinsic inversion symmetry breaking at the LSMO interfaces, plays a major role in the observed depressed magnetotransport properties in manganite-based magnetic tunneling junctions and explains the origin of the so-called dead layer.
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Affiliation(s)
- S Valencia
- Helmholtz-Zentrum-Berlin, Albert-Einstein-Str. 15, 12489 Berlin, Germany
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6
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Chu MW, Chen CH. Chemical mapping and quantification at the atomic scale by scanning transmission electron microscopy. ACS NANO 2013; 7:4700-4707. [PMID: 23799301 DOI: 10.1021/nn4023558] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
With innovative modern material-growth methods, a broad spectrum of fascinating materials with reduced dimensions-ranging from single-atom catalysts, nanoplasmonic and nanophotonic materials to two-dimensional heterostructural interfaces-is continually emerging and extending the new frontiers of materials research. A persistent central challenge in this grand scientific context has been the detailed characterization of the individual objects in these materials with the highest spatial resolution, a problem prompting the need for experimental techniques that integrate both microscopic and spectroscopic capabilities. To date, several representative microscopy-spectroscopy combinations have become available, such as scanning tunneling microscopy, tip-enhanced scanning optical microscopy, atom probe tomography, scanning transmission X-ray microscopy, and scanning transmission electron microscopy (STEM). Among these tools, STEM boasts unique chemical and electronic sensitivity at unparalleled resolution. In this Perspective, we elucidate the advances in STEM and chemical mapping applications at the atomic scale by energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy with a focus on the ultimate challenge of chemical quantification with atomic accuracy.
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Affiliation(s)
- Ming-Wen Chu
- Center for Condensed Matter Sciences, National Taiwan University, Taipei 106, Taiwan.
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7
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Pesquera D, Herranz G, Barla A, Pellegrin E, Bondino F, Magnano E, Sánchez F, Fontcuberta J. Surface symmetry-breaking and strain effects on orbital occupancy in transition metal perovskite epitaxial films. Nat Commun 2013; 3:1189. [PMID: 23149734 DOI: 10.1038/ncomms2189] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Accepted: 10/04/2012] [Indexed: 11/09/2022] Open
Abstract
The electron occupancy of 3d-orbitals determines the properties of transition metal oxides. This can be achieved, for example, through thin-film heterostructure engineering of ABO(3) oxides, enabling emerging properties at interfaces. Interestingly, epitaxial strain may break the degeneracy of 3d-e(g) and t(2g) orbitals, thus favoring a particular orbital filling with consequences for functional properties. Here we disclose the effects of symmetry breaking at free surfaces of ABO(3) perovskite epitaxial films and show that it can be combined with substrate-induced epitaxial strain to tailor at will the electron occupancy of in-plane and out-of-plane surface electronic orbitals. We use X-ray linear dichroism to monitor the relative contributions of surface, strain and atomic terminations to the occupancy of 3z(2)-r(2) and x(2)-y(2) orbitals in La(2/3)Sr(1/3)MnO(3) films. These findings open the possibility of an active tuning of surface electronic and magnetic properties as well as chemical properties (catalytic reactivity, wettability and so on).
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Affiliation(s)
- D Pesquera
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, Bellaterra 08193, Spain
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8
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Lee JS, Kao CC, Nelson CS, Jang H, Ko KT, Kim SB, Choi YJ, Cheong SW, Smadici S, Abbamonte P, Park JH. Fragile magnetic ground state in half-doped LaSr2Mn2O7. PHYSICAL REVIEW LETTERS 2011; 107:037206. [PMID: 21838401 DOI: 10.1103/physrevlett.107.037206] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Indexed: 05/31/2023]
Abstract
We investigated the orbital and antiferromagnetic ordering behaviors of the half-doped bilayer manganite La(2-2x)Sr(1+2x)Mn2O7 (x ≃ 0.5) by using Mn L(2,3)-edge resonant soft x-ray scattering. Resonant soft x-ray scattering reveals the CE-type orbital order below T(oo) ≃ 220 K, which shows partial melting behavior below T(m) ≃ 165 K. We also found coexistence CE- and A-type antiferromagnetic orders. Both orders involve the CE-type orbital order with nearly the same orbital character and are coupled with each other. These results manifest that the ground state with the CE-type antiferromagnetic order is easily susceptible to destabilization into the A-type one even with a small fluctuation of the doping level, as suggested by the extremely narrow magnetic phase boundaries at x ≃ 0.5±0.005.
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Affiliation(s)
- J-S Lee
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
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9
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Rościszewski K, Oleś AM. Jahn-Teller distortions and the magnetic order in the perovskite manganites. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:425601. [PMID: 21403311 DOI: 10.1088/0953-8984/22/42/425601] [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
We introduce an effective model for e(g) electrons to describe three-dimensional perovskite (La(1 - x)Sr(x)MnO(3) and La(1 - x)Ca(x)MnO(3)) manganites and study the magnetic and orbital order on a 4 × 4 × 4 cluster using correlated wavefunctions. The model includes the kinetic energy, and on-site Coulomb interactions for e(g) electrons, antiferromagnetic superexchange interaction between S = 3/2 core spins, and the coupling between e(g) electrons and Jahn-Teller modes. The model reproduces the experimentally observed magnetic order: (i) an A-type antiferromagnetic phase in the undoped insulator LaMnO(3), with alternating e(g) orbitals and with small Jahn-Teller distortions, changing to a conducting phase at 32 GPa pressure, and (ii) ferromagnetic order in one-eighth-doped La(7/8)Sr(1/8)MnO(3) and in quarter-doped La(3/4)Sr(1/4)MnO(3) compounds. For half-doped La(1/2)Ca(1/2)MnO(3) one finds a competition between a ferromagnetic conductor and the CE insulating phase; the latter is stabilized by the Jahn-Teller coupling being two times larger than for the strontium-doped compound. Altogether, there is a subtle balance between all Hamiltonian parameters and the phase diagram is quite sensitive to the precise values they take.
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Affiliation(s)
- Krzysztof Rościszewski
- Marian Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, Kraków, Poland.
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10
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X-ray spectroscopy of lanthanum manganites: Nature of doping holes, correlation effects, and orbital ordering. J STRUCT CHEM+ 2009. [DOI: 10.1007/s10947-008-0201-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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11
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Ma C, Yang HX, Zeng LJ, Li ZA, Zhang Y, Qin YB, Li JQ. Effects of layered structural features on charge/orbital ordering in (La, Sr)(n+1)Mn(n)O(3n+1) (n = 1 and 2). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:045601. [PMID: 21715815 DOI: 10.1088/0953-8984/21/4/045601] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The charge/orbital ordering (COO) of the layered mixed-valence manganites (La,Sr)(n+1)Mn(n)O(3n+1) (n = 1 and 2) is examined by first-principles calculations and discussed in comparison with the La(0.5)Ca(0.5)MnO(3) perovskite phase ([Formula: see text]). The results demonstrated that the layered structural features could yield not only visibly weak coupling between Mn-O layers but also various features in the orbital ordering associated with different types of local structural distortions. In both La(0.5)Sr(1.5)MnO(4) (n = 1) and LaSr(2)Mn(2)O(7) (n = 2) phases, the orbital ordering can be chiefly assigned to the d(x(2)-y(2)) orbital, in contrast with the zigzag-type d(z(2)) orbital ordering in the [Formula: see text] perovskite phase. Our theoretical analysis shows that a variety of essential factors, including the local structural distortions of the MnO(6) octahedra, the on-site Coulomb interaction, and magnetic interaction, have to be properly considered in order to achieve acceptable COO ground states for the layered variants in (La,Sr)(n+1)Mn(n)O(3n+1).
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Affiliation(s)
- C Ma
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, People's Republic of China
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12
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Hossain MA, Hu Z, Haverkort MW, Burnus T, Chang CF, Klein S, Denlinger JD, Lin HJ, Chen CT, Mathieu R, Kaneko Y, Tokura Y, Satow S, Yoshida Y, Takagi H, Tanaka A, Elfimov IS, Sawatzky GA, Tjeng LH, Damascelli A. Crystal-field level inversion in lightly Mn-doped Sr3Ru2O7. PHYSICAL REVIEW LETTERS 2008; 101:016404. [PMID: 18764131 DOI: 10.1103/physrevlett.101.016404] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2008] [Indexed: 05/26/2023]
Abstract
Sr3(Ru(1-x)Mnx)2O7, in which 4d-Ru is substituted by the more localized 3d-Mn, is studied by x-ray dichroism and spin-resolved density functional theory. We find that Mn impurities do not exhibit the same 4+ valence of Ru, but act as 3+ acceptors; the extra eg electron occupies the in-plane 3d(x2-y2) orbital instead of the expected out-of-plane 3d(3z2-r2). We propose that the 3d-4d interplay, via the ligand oxygen orbitals, is responsible for this crystal-field level inversion and the material's transition to an antiferromagnetic, possibly orbitally ordered, low-temperature state.
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Affiliation(s)
- M A Hossain
- Department of Physics & Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
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13
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Tebano A, Aruta C, Sanna S, Medaglia PG, Balestrino G, Sidorenko AA, De Renzi R, Ghiringhelli G, Braicovich L, Bisogni V, Brookes NB. Evidence of orbital reconstruction at interfaces in ultrathin La0.67Sr0.33MnO3 films. PHYSICAL REVIEW LETTERS 2008; 100:137401. [PMID: 18517994 DOI: 10.1103/physrevlett.100.137401] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2007] [Indexed: 05/26/2023]
Abstract
Linear dichroism (LD) in x-ray absorption, diffraction, transport, and magnetization measurements on thin La(0.7)Sr(0.3)MnO(3) films grown on different substrates, allow identification of a peculiar interface effect, related just to the presence of the interface. We report the LD signature of preferential 3d-e(g)(3z(2)-r(2)) occupation at the interface, suppressing the double exchange mechanism. This surface orbital reconstruction is opposite to that favored by residual strain and is independent of dipolar fields, the chemical nature of the substrate and the presence of capping layers.
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Affiliation(s)
- A Tebano
- CNR-INFM Coherentia and Dipartimento di Ingegneria Meccanica, Università di Roma Tor Vergata, Via del Politecnico 1, 00133 Roma, Italy
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14
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Stamm C, Kachel T, Pontius N, Mitzner R, Quast T, Holldack K, Khan S, Lupulescu C, Aziz EF, Wietstruk M, Dürr HA, Eberhardt W. Femtosecond modification of electron localization and transfer of angular momentum in nickel. NATURE MATERIALS 2007; 6:740-3. [PMID: 17721541 DOI: 10.1038/nmat1985] [Citation(s) in RCA: 163] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2007] [Accepted: 07/20/2007] [Indexed: 05/16/2023]
Abstract
The rapidly increasing information density required of modern magnetic data storage devices raises the question of the fundamental limits in bit size and writing speed. At present, the magnetization reversal of a bit can occur as quickly as 200 ps (ref. 1). A fundamental limit has been explored by using intense magnetic-field pulses of 2 ps duration leading to a non-deterministic magnetization reversal. For this process, dissipation of spin angular momentum to other degrees of freedom on an ultrafast timescale is crucial. An even faster regime down to 100 fs or below might be reached by non-thermal control of magnetization with femtosecond laser radiation. Here, we show that an efficient novel channel for angular momentum dissipation to the lattice can be opened by femtosecond laser excitation of a ferromagnet. For the first time, the quenching of spin angular momentum and its transfer to the lattice with a time constant of 120+/-70 fs is determined unambiguously with X-ray magnetic circular dichroism. We report the first femtosecond time-resolved X-ray absorption spectroscopy data over an entire absorption edge, which are consistent with an unexpected increase in valence-electron localization during the first 120+/-50 fs, possibly providing the driving force behind femtosecond spin-lattice relaxation.
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Affiliation(s)
- C Stamm
- BESSY GmbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany
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15
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Rościszewski K, Oleś AM. Interplay between the orbital and magnetic order in monolayer La(1-x)Sr(1+x)MnO(4) manganites. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2007; 19:186223. [PMID: 21691004 DOI: 10.1088/0953-8984/19/18/186223] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
A two-dimensional model which describes e(g) electrons in a monolayer of an undoped and half doped manganite La(1-x)Sr(1+x)MnO(4) is studied using correlated wavefunctions. The effective Hamiltonian takes into account the kinetic energy, the crystal field splitting between x(2)-y(2) and 3z(2)-r(2) orbitals, and on-site Coulomb interactions for e(g) electrons. They interact with S = 3/2 spins due to t(2g) electrons, which are treated as frozen core spins. Furthermore, the model includes antiferromagnetic superexchange interaction between core spins, and the coupling between e(g) electrons and Jahn-Teller modes. The model reproduces the antiferromagnetic order in the undoped LaSrMnO(4) compound, with occupied 3z(2)-r(2) orbitals and elongated MnO(6) octahedra along the direction perpendicular to the Mn-O plane. In half doped La(0.5)Sr(1.5)MnO(4) manganite one finds robust chequerboard-like charge order using realistic parameters. However, the experimentally observed CE phase is more difficult to stabilize, and we discuss the necessary conditions to obtain it within the present model. Altogether, we conclude that the Jahn-Teller effect plays a crucial role in the entire regime of doping.
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Affiliation(s)
- Krzysztof Rościszewski
- Marian Smoluchowski Institute of Physics, Jagellonian University, Reymonta 4, PL-30059 Kraków, Poland
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van Veenendaal M, McNulty I. Prediction of strong dichroism induced by x rays carrying orbital momentum. PHYSICAL REVIEW LETTERS 2007; 98:157401. [PMID: 17501381 DOI: 10.1103/physrevlett.98.157401] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2006] [Indexed: 05/15/2023]
Abstract
We predict the presence of strong dichroic effects induced by x-ray beams carrying orbital angular momentum (OAM). Taking the difference between spectra obtained with positive and negative OAM states allows the separation of quadrupolar from dipolar transitions at, e.g., the transition-metal K edges, enabling the study of the unoccupied states in the absence of strong core-hole effects. We study the dependence of OAM-induced x-ray dichroism on different polarization vectors and derive sum rules relating the integrated intensity to ground-state hole densities. Calculations of spectral line shapes for cuprates, manganites, and ruthenates confirm the strong OAM-induced dichroism and indicate the potential of this new spectroscopy in the fields of orbital physics and magnetism.
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Kuepper K, Bondino F, Prince KC, Zangrando M, Zacchigna M, Takás AF, Crainic T, Matteucci M, Parmigiani F, Winiarski A, Galakhov VR, Mukovskii YM, Neumann M. Direct Investigation of Orbital Ordering in a Colossal Magnetoresistance Manganite by Means of X-ray Linear Dichroism at the Mn L Edge. J Phys Chem B 2005; 109:15667-70. [PMID: 16852985 DOI: 10.1021/jp052762s] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have investigated for the first time the orbital ordering in a three-dimensional colossal magnetoresistance manganite, namely La(7/8)Sr(1/8)MnO3, by applying soft X-ray linear dichroism (XLD) to the Mn L edge. We found that the cooperative Jahn-Teller distorted orthorhombic phase, which is present at a temperature of 240 K, is probably accompanied by a predominantly cross type (x2 - z2)/(y2 - z2) orbital ordering. This result is discussed in the light of different exchange interaction models.
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Iga F, Tsubota M, Sawada M, Huang HB, Kura S, Takemura M, Yaji K, Nagira M, Kimura A, Jo T, Takabatake T, Namatame H, Taniguchi M. Determination of the orbital polarization in YTiO3 by using soft X-ray linear dichroism. PHYSICAL REVIEW LETTERS 2004; 93:257207. [PMID: 15697937 DOI: 10.1103/physrevlett.93.257207] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2004] [Indexed: 05/24/2023]
Abstract
We report measurements of linear dichroism in x-ray absorption at Ti L(2,3) edges of a Mott-insulating ferromagnet YTiO3, where orbital ordering occurs in the triply degenerate Ti 3d t(2g) states. Dichroic spectra and their integrated intensities are obtained for the incident electric field with polarizations parallel to a, b, and c axes. The comparison of the spectra with atomic multiplet calculations removes the ambiguity about the orbital polarization, i.e., the relative weights of |xy>, |yz>, and |zx> orbits, which are crucial for the origin of ferromagnetism. The result is consistent with the previous analysis of nuclear magnetic resonance in the Mizokawa-Fujimori scheme.
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Affiliation(s)
- F Iga
- Department of Quantum Matter, ADSM, Hiroshima University, Higashi-Hiroshima, 739-8530, Japan
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Jeng HT, Guo GY, Huang DJ. Charge-orbital ordering and Verwey transition in magnetite. PHYSICAL REVIEW LETTERS 2004; 93:156403. [PMID: 15524911 DOI: 10.1103/physrevlett.93.156403] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2004] [Indexed: 05/12/2023]
Abstract
Local density approximation + Hubbard U (LDA + U) band structure calculations reveal that magnetite (Fe3O4) forms an insulating charge-orbital-ordered state below the Verwey transition temperature. The calculated charge ordering is in good agreement with that inferred from recent experiments. We found an associated t(2g) orbital ordering on the octahedral Fe2+ sublattice. Such an orbital ordering results primarily from the on-site Coulomb interaction. This finding unravels such fundamental issues about the Verwey transition as the mechanism for the charge ordering and for the formation of the insulating gap, as well as the nonobedience of the Anderson's criterion for the charge ordering.
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Affiliation(s)
- Horng-Tay Jeng
- Physics Division, National Center for Theoretical Sciences, Hsinchu 300, Taiwan.
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