Direct Determination of Exchange Parameters in ${\mathrm{Cs}}_{2}{\mathrm{CuBr}}_{4}$ and ${\mathrm{Cs}}_{2}{\mathrm{CuCl}}_{4}$: High-Field Electron-Spin-Resonance Studies

Direct Determination of Exchange Parameters in ${Cs}_{2} {CuBr}_{4}$ and ${Cs}_{2} {CuCl}_{4}$ : High-Field Electron-Spin-Resonance Studies

S. A. Zvyagin, D. Kamenskyi, M. Ozerov, J. Wosnitza, M. Ikeda, T. Fujita, M. Hagiwara, A. I. Smirnov, T. A. Soldatov, A. Ya. Shapiro, J. Krzystek, R. Hu, H. Ryu, C. Petrovic, and M. E. Zhitomirsky

Phys. Rev. Lett. 112, 077206 – Published 20 February 2014

Abstract

Spin- $1 / 2$ Heisenberg antiferromagnets ${Cs}_{2} {CuCl}_{4}$ and ${Cs}_{2} {CuBr}_{4}$ with distorted triangular-lattice structures are studied by means of electron spin resonance spectroscopy in magnetic fields up to the saturation field and above. In the magnetically saturated phase, quantum fluctuations are fully suppressed, and the spin dynamics is defined by ordinary magnons. This allows us to accurately describe the magnetic excitation spectra in both materials and, using the harmonic spin-wave theory, to determine their exchange parameters. The viability of the proposed method was proven by applying it to ${Cs}_{2} {CuCl}_{4}$ , yielding $J / k_{B} = 4.7 (2) K$ , $J^{'} / k_{B} = 1.42 (7) K$ , [ $J^{'} / J ≃ 0.30$ ] and revealing good agreement with inelastic neutron-scattering results. For the isostructural ${Cs}_{2} {CuBr}_{4}$ , we obtain $J / k_{B} = 14.9 (7) K$ , $J^{'} / k_{B} = 6.1 (3) K$ , [ $J^{'} / J ≃ 0.41$ ], providing exact and conclusive information on the exchange couplings in this frustrated spin system.

Received 12 December 2013

DOI:https://doi.org/10.1103/PhysRevLett.112.077206

Authors & Affiliations

S. A. Zvyagin¹, D. Kamenskyi^1,*, M. Ozerov¹, J. Wosnitza^1,2, M. Ikeda³, T. Fujita³, M. Hagiwara³, A. I. Smirnov⁴, T. A. Soldatov⁵, A. Ya. Shapiro⁶, J. Krzystek⁷, R. Hu^8,†, H. Ryu^8,9, C. Petrovic^8,9, and M. E. Zhitomirsky¹⁰

¹Dresden High Magnetic Field Laboratory (HLD), Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
²Institüt fur Festkörperphysik, TU Dresden, 01068 Dresden, Germany
³KYOKUGEN, Osaka University, Toyonaka, Osaka 560-8531, Japan
⁴P.L. Kapitza Institute for Physical Problems, RAS, 119334 Moscow, Russia
⁵Moscow Institute for Physics and Technology, 141700 Dolgoprudnyi, Russia
⁶A.V. Shubnikov Institute of Crystallography, RAS, 119333, Moscow, Russia
⁷National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, USA
⁸Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
⁹Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794-3800, USA
¹⁰Service de Physique Statistique, Magnétisme et Supraconductivité, UMR-E9001 CEA-INAC/UJF, 38054 Grenoble Cedex 9, France

^*Present address: Radboud University Nijmegen, Institute for Molecules and Materials, High Field Magnet Laboratory, 6500 GL Nijmegen, Netherlands
^†Present address: Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854, USA

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Vol. 112, Iss. 7 — 21 February 2014

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Physical Review Letters

Direct Determination of Exchange Parameters in Cs2CuBr4 and Cs2CuCl4: High-Field Electron-Spin-Resonance Studies

S. A. Zvyagin, D. Kamenskyi, M. Ozerov, J. Wosnitza, M. Ikeda, T. Fujita, M. Hagiwara, A. I. Smirnov, T. A. Soldatov, A. Ya. Shapiro, J. Krzystek, R. Hu, H. Ryu, C. Petrovic, and M. E. Zhitomirsky

Phys. Rev. Lett. 112, 077206 – Published 20 February 2014

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Direct Determination of Exchange Parameters in ${Cs}_{2} {CuBr}_{4}$ and ${Cs}_{2} {CuCl}_{4}$ : High-Field Electron-Spin-Resonance Studies