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Sampson G, Bristowe NC, Carr ST, Saib A, Stenning GBG, Clark ER, Saines PJ. Quantum Spin‐1/2 Dimers in a Low‐Dimensional Tetrabromocuprate Magnet. Chemistry 2022; 28:e202200855. [PMID: 35357728 PMCID: PMC9323490 DOI: 10.1002/chem.202200855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Indexed: 11/07/2022]
Abstract
This work describes a homometallic spin‐1/2
tetrabromocuprate adopting a bilayer structure. Magnetic‐susceptibility measurements show a broad maximum centred near 70 K, with fits to this data using a Heisenberg model consistent with strong antiferromagnetic coupling between neighbouring copper atoms in different layers of the bilayer. There are further weak intralayer ferromagnetic interactions between copper cations in neighbouring dimers. First‐principles calculations are consistent with this, but suggest there is only significant magnetic coupling within one direction of a layer; this would suggest the presence of a spin ladder within the bilayer with antiferromagnetic rung and weaker ferromagnetic rail couplings.
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Affiliation(s)
- Gavin Sampson
- School of Physical SciencesUniversity of KentCanterburyKentCT2 7NHUK
| | - Nicholas C. Bristowe
- School of Physical SciencesUniversity of KentCanterburyKentCT2 7NHUK
- Centre for Materials PhysicsDurham UniversitySouth RoadDurhamDH1 3LEUK
| | - Sam T. Carr
- School of Physical SciencesUniversity of KentCanterburyKentCT2 7NHUK
| | - Asad Saib
- School of Physical SciencesUniversity of KentCanterburyKentCT2 7NHUK
| | - Gavin B. G. Stenning
- ISIS Neutron and Muon SourceRutherford Appleton Laboratory Harwell Science and Innovation CampusDidcotOX11 0QXUK
| | - Ewan R. Clark
- School of Physical SciencesUniversity of KentCanterburyKentCT2 7NHUK
| | - Paul J. Saines
- School of Physical SciencesUniversity of KentCanterburyKentCT2 7NHUK
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Kim JH, Jain A, Reehuis M, Khaliullin G, Peets DC, Ulrich C, Park JT, Faulhaber E, Hoser A, Walker HC, Adroja DT, Walters AC, Inosov DS, Maljuk A, Keimer B. Competing exchange interactions on the verge of a metal-insulator transition in the two-dimensional spiral magnet Sr3Fe2O7. PHYSICAL REVIEW LETTERS 2014; 113:147206. [PMID: 25325658 DOI: 10.1103/physrevlett.113.147206] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Indexed: 06/04/2023]
Abstract
We report a neutron scattering study of the magnetic order and dynamics of the bilayer perovskite Sr(3)Fe(2)O(7), which exhibits a temperature-driven metal-insulator transition at 340 K. We show that the Fe(4+) moments adopt incommensurate spiral order below T(N) = 115 K and provide a comprehensive description of the corresponding spin-wave excitations. The observed magnetic order and excitation spectra can be well understood in terms of an effective spin Hamiltonian with interactions ranging up to third-nearest-neighbor pairs. The results indicate that the helical magnetism in Sr(3)Fe(2)O(7) results from competition between ferromagnetic double-exchange and antiferromagnetic superexchange interactions whose strengths become comparable near the metal-insulator transition. They thus confirm a decades-old theoretical prediction and provide a firm experimental basis for models of magnetic correlations in strongly correlated metals.
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Affiliation(s)
- J-H Kim
- Max-Planck-Institut für Festkörperforschung, D-70569 Stuttgart, Germany
| | - Anil Jain
- Max-Planck-Institut für Festkörperforschung, D-70569 Stuttgart, Germany and Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India
| | - M Reehuis
- Helmholtz-Zentrum Berlin für Materialien und Energie, D-14109 Berlin, Germany
| | - G Khaliullin
- Max-Planck-Institut für Festkörperforschung, D-70569 Stuttgart, Germany
| | - D C Peets
- Max-Planck-Institut für Festkörperforschung, D-70569 Stuttgart, Germany
| | - C Ulrich
- Max-Planck-Institut für Festkörperforschung, D-70569 Stuttgart, Germany and School of Physics, University of New South Wales, Sydney, New South Wales 2052, Australia and Australian Nuclear Science and Technology Organisation, Lucas Heights, New South Wales 2234, Australia
| | - J T Park
- Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM-II), D-85748 Garching, Germany
| | - E Faulhaber
- Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM-II), D-85748 Garching, Germany
| | - A Hoser
- Helmholtz-Zentrum Berlin für Materialien und Energie, D-14109 Berlin, Germany
| | - H C Walker
- ISIS Facility, STFC, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11-0QX, United Kingdom
| | - D T Adroja
- ISIS Facility, STFC, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11-0QX, United Kingdom and Physics Department, Highly Correlated Matter Research Group, University of Johannesburg, P.O. Box 524, Auckland Park 2006, South Africa
| | - A C Walters
- Max-Planck-Institut für Festkörperforschung, D-70569 Stuttgart, Germany
| | - D S Inosov
- Max-Planck-Institut für Festkörperforschung, D-70569 Stuttgart, Germany and Institut für Festkörperphysik, TU Dresden, D-01069 Dresden, Germany
| | - A Maljuk
- Max-Planck-Institut für Festkörperforschung, D-70569 Stuttgart, Germany and Leibniz Institut für Festkörper-und Werkstoffforschung, D-01171 Dresden, Germany
| | - B Keimer
- Max-Planck-Institut für Festkörperforschung, D-70569 Stuttgart, Germany
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Kim J, Said AH, Casa D, Upton MH, Gog T, Daghofer M, Jackeli G, van den Brink J, Khaliullin G, Kim BJ. Large spin-wave energy gap in the bilayer iridate Sr3Ir2O7: evidence for enhanced dipolar interactions near the mott metal-insulator transition. PHYSICAL REVIEW LETTERS 2012; 109:157402. [PMID: 23102367 DOI: 10.1103/physrevlett.109.157402] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Indexed: 05/23/2023]
Abstract
Using resonant inelastic x-ray scattering, we observe in the bilayer iridate Sr3Ir2O7, a spin-orbit coupling driven magnetic insulator with a small charge gap, a magnon gap of ≈92 meV for both acoustic and optical branches. This exceptionally large magnon gap exceeds the total magnon bandwidth of ≈70 meV and implies a marked departure from the Heisenberg model, in stark contrast to the case of the single-layer iridate Sr2IrO4. Analyzing the origin of these observations, we find that the giant magnon gap results from bond-directional pseudodipolar interactions that are strongly enhanced near the metal-insulator transition boundary. This suggests that novel magnetism, such as that inspired by the Kitaev model built on the pseudodipolar interactions, may emerge in small charge-gap iridates.
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Affiliation(s)
- Jungho Kim
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
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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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Freeland JW, Kavich JJ, Gray KE, Ozyuzer L, Zheng H, Mitchell JF, Warusawithana MP, Ryan P, Zhai X, Kodama RH, Eckstein JN. Suppressed magnetization at the surfaces and interfaces of ferromagnetic metallic manganites. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2007; 19:315210. [PMID: 21694110 DOI: 10.1088/0953-8984/19/31/315210] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
What happens to ferromagnetism at the surfaces and interfaces of manganites? With the competition between charge, spin, and orbital degrees of freedom, it is not surprising that the surface behaviour may be profoundly different to that of the bulk. Using a powerful combination of two surface probes, tunnelling and polarized x-ray interactions, this paper reviews our work on the nature of the electronic and magnetic states at manganite surfaces and interfaces. The general observation is that ferromagnetism is not the lowest energy state at the surface or interface, which results in a suppression or even loss of ferromagnetic order at the surface. Two cases will be discussed ranging from the surface of the quasi-2D bilayer manganite (La(2-2x)Sr(1+2x)Mn(2)O(7)) to the 3D perovskite (La(2/3)Sr(1/3)MnO(3))/SrTiO(3) interface. For the bilayer manganite, which is ferromagnetic and conducting in the bulk, these probes present clear evidence for an intrinsic insulating non-ferromagnetic surface layer atop adjacent subsurface layers that display the full bulk magnetization. This abrupt intrinsic magnetic interface is attributed to the weak inter-bilayer coupling native to these quasi-two-dimensional materials. This is in marked contrast to the situation for the non-layered manganite system (La(2/3)Sr(1/3)MnO(3)/SrTiO(3)), whose magnetization near the interface is less than half the bulk value at low temperatures and decreases with increasing temperature at a faster rate than that for the bulk.
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Affiliation(s)
- J W Freeland
- Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA
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Schwieger S, Kienert J, Lenz K, Lindner J, Baberschke K, Nolting W. Spin-wave excitations: the main source of the temperature dependence of interlayer exchange coupling in nanostructures. PHYSICAL REVIEW LETTERS 2007; 98:057205. [PMID: 17358895 DOI: 10.1103/physrevlett.98.057205] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2006] [Indexed: 05/14/2023]
Abstract
Quantum mechanical calculations based on an extended Heisenberg model are compared with ferromagnetic resonance experiments on prototype trilayer systems Ni(7)/Cu(n)/Co(2)/Cu(001) in order to determine and separate for the first time quantitatively the sources of the temperature dependence of interlayer exchange coupling. Magnon excitations are responsible for about 75% of the reduction of the coupling strength from zero to room temperature. The remaining 25% are due to temperature effects in the effective quantum well and the spacer-magnet interfaces.
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Affiliation(s)
- S Schwieger
- Theoretische Physik I, Technische Universität Ilmenau, Postfach 10 05 65, 98684 Ilmenau, Germany
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Tomimoto S, Matsubara M, Ogasawara T, Okamoto H, Kimura T, Tokura Y. Optical control of the magnetic anisotropy of ferromagnetic bilayered manganites. PHYSICAL REVIEW LETTERS 2007; 98:017402. [PMID: 17358505 DOI: 10.1103/physrevlett.98.017402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2006] [Indexed: 05/14/2023]
Abstract
Optical manipulation of the magnetic anisotropy is demonstrated for bilayered manganites, La2-2xSr1+2xMn2O7, by means of femtosecond Kerr-rotation measurements. Upon the photoexcitation on the x=0.32 crystal, the magnetization exhibits the precessional motion for about 1 ns, revealing the directional change of the magnetocrystalline anisotropy from the c axis to the ab plane. This change of the anisotropy induces the nonthermal decrease of the c-axis magnetization component for about 1 ns.
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Affiliation(s)
- S Tomimoto
- Correlated Electron Research Center, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan
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Chatterji T, Demmel F, Chaudhury R. Spin dynamics of the quasi-two-dimensional ferromagnetic bilayer manganite. PHYSICA B: CONDENSED MATTER 2006; 385-386:428-431. [DOI: 10.1016/j.physb.2006.05.143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/19/2023]
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Endoh Y, Hiraka H, Tomioka Y, Tokura Y, Nagaosa N, Fujiwara T. Orbital nature of ferromagnetic magnons in manganites. PHYSICAL REVIEW LETTERS 2005; 94:017206. [PMID: 15698129 DOI: 10.1103/physrevlett.94.017206] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2004] [Indexed: 05/24/2023]
Abstract
Magnon excitation in a ferromagnetic state of Sm(0.55)Sr(0.45)MnO(3) located on the verge of the metal-insulator transition has been studied in terms of the neutron scattering experiment. The anomalous magnon dispersion with the zone-boundary softening is well described by the Heisenberg model with extended exchange coupling constants J(s). In particular the fourth neighbor coupling J(4) is as large as 0.6 times the nearest neighbor one J(1). Theoretical analysis based on the local density approximation + Hubbard U band calculation reveals that this one-dimensional exchange path is due to the (3z(2)-r(2))-type orbital correlation, in sharp contrast to previous proposals.
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Affiliation(s)
- Y Endoh
- Institute for Materials Research, Tohoku University, Katahira, Sendai 980-8577, Japan
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Blundell SJ, Stride JA, Brooks ML, Steer CA, Nair SP, Battle PD, Rosseinsky MJ. The observation of magnetic excitations in a single layered and a bilayered brownmillerite. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2005; 17:99-104. [PMID: 21690672 DOI: 10.1088/0953-8984/17/1/010] [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 describe the results of an inelastic neutron scattering measurement of the magnetic excitations in SrCaGaMnO(5+δ), a quasi-two-dimensional compound whose structure consists of layers of MnO(6) octahedra separated by layers of GaO(4) tetrahedra (the brownmillerite structure), and Ca(2.5)Sr(0.5)Mn(2)GaO(8), a bilayered brownmillerite. In both materials, a band of magnetic scattering appears below the magnetic ordering temperature which can be associated with magnon excitations. Our measurements allow us to provide an estimate for the intraplane exchange constant in both materials, which we find to be 3.4(4) meV for SrCaGaMnO(5+δ) and 2.2(4) meV for Ca(2.5)Sr(0.5)Mn(2)GaO(8).
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Affiliation(s)
- Stephen J Blundell
- Department of Physics, Clarendon Laboratory, Oxford University, Parks Road, Oxford OX1 3PU, UK
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Moussa F, Hennion M, Wang F, Gukasov A, Suryanarayanan R, Apostu M, Revcolevschi A. Field-induced ferromagnetic metallic state in the bilayer manganite (La0.4Pr0.6)1.2Sr1.8Mn2O7, probed by neutron scattering. PHYSICAL REVIEW LETTERS 2004; 93:107202. [PMID: 15447443 DOI: 10.1103/physrevlett.93.107202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2004] [Indexed: 05/24/2023]
Abstract
The bilayer manganite La1.2Sr1.8Mn2O7 exhibits a phase transition from a paramagnetic insulating (PI) to a ferromagnetic metallic (FM) state with a colossal magnetoresistance (CMR) effect. Upon 60% Pr substitution, magnetic order and PI to FM transition are suppressed. Application of a moderate magnetic field restores an FM state with a CMR effect. Neutron scattering by a single crystal of (La0.4Pr0.6)1.2Sr1.8Mn2O7, under a magnetic field of 5 T, has revealed a long-range and homogeneous ferromagnetic order. In the PI phase, under zero field, correlated lattice polarons have been detected. At 28 K, under 5 T, the spin wave dispersion curve determines an in-plane isotropic spin wave stiffness constant of 146 meV A(2). So the magnetic field not only generates a homogeneous ferromagnetic ground state, but also restores a magnetic coupling characteristic of FM CMR manganites.
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Affiliation(s)
- F Moussa
- Laboratoire Léon Brillouin, CEA-CNRS, CE-Saclay, F-91191 Gif-sur-Yvette Cedex, France
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Manganites. ACTA ACUST UNITED AC 2004. [DOI: 10.1007/978-3-662-09298-9_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/21/2023]
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