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Article Dans Une Revue Physical Review Letters Année : 2014

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

Résumé

Spin-1/2 Heisenberg antiferromagnets Cs2CuCl4 and Cs2CuBr4 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 Cs2CuCl4, yielding J/k(B) = 4.7(2) K, J'/k(B) = 1.42(7) K, [J'/J similar or equal to 0.30] and revealing good agreement with inelastic neutron-scattering results. For the isostructural Cs2CuBr4, we obtain J/k(B) = 14.9(7) K, J'/k(B) = 6.1(3) K, [J'/J similar or equal to 0.41], providing exact and conclusive information on the exchange couplings in this frustrated spin system.

Dates et versions

hal-02095634 , version 1 (10-04-2019)

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S. A. Zvyagin, D. Kamenskyi, M. Ozerov, J. Wosnitza, M. Ikeda, et al.. Direct Determination of Exchange Parameters in Cs 2 CuBr 4 and Cs 2 CuCl 4 : High-Field Electron-Spin-Resonance Studies. Physical Review Letters, 2014, 112 (7), pp.077206. ⟨10.1103/PhysRevLett.112.077206⟩. ⟨hal-02095634⟩
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