Direct Determination of Exchange Parameters inCs2CuBr4andCs2<

Abstract

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/kB=4.7(2) K, J'/kB=1.42(7) K, [J'/J≃0.30] and revealing good agreement with inelastic neutron-scattering results. For the isostructural Cs2CuBr4, we obtain J/kB=14.9(7) K, J'/kB=6.1(3) K, [J'/J≃0.41], providing exact and conclusive information on the exchange couplings in this frustrated spin system.

Direct observation of spin-quadrupolar excitations in Sr2CoGe2O7 by high-field electron spin resonance

“…10), as it is coupled to theP (π,π) andM (π,π) only (lowest row in Tab II). Let us also mention that the D 1 magnon mode is usually not observed in the ESR spectra, unless Dzyaloshinskii-Moriya interaction or staggered g-tensor is present [38]. In SCGO, not only the staggered g-tensor, but also the staggered component of the polarization can lead to absorption at q = (π, π).…”

Properties of spin-12triangular-lattice antiferromagnetsCuY2Ge2O8andCho1, Kratochvílová2, Sim3 et al. 2017Phys. Rev. B

“…This argument makes the 2D magnetic systems interesting and explains why, as compared with either 1D or 3D systems, 2D systems have a tendency of singlet and Néel-ordered ground states found in close proximity in the parameter space of physical quantities [3][4][5][6][7][8][9][10][11][12][13][14]. In addition, geometrical frustration can further prevent a system from ordering in either simple Néel type or singlet type states and thus can lead to exotic physical phenomena at low temperatures [6][7][8][9][10][11][12][13][14][15][16][17][18]. This is especially true for 2D triangular lattice systems as compared with 2D square lattice systems, the latter of which is often found in the Néel-ordered state due to the weakness of the diagonal next-nearest neighbor interactions [19].…”

Phase diagram of thespin−12triangularJ1−J2Heisenberg model on a three-leg cylinder

“…However, studies of this model have failed to find an RVB state and the evidence [17,18] is now very strong that for the pure isotropic model with nearest-neighbor interactions the ground state is a 120 • magnetically ordered state [1]. Variants of the THM describe some properties of organic materials [8,9] such as κ-(BEDT-TTF) 2 Cu 2 (CN) 3 3 [20,21] and also some quasi-two-dimensional inorganic materials [8,9,[22][23][24][25] In one dimension the prototypical frustrated system is the zig-zag chain, which has an exact solution at the MajumdarGhosh point [3,5] where the NN coupling is twice the next-nearest-neighbor (NNN) coupling. The ground state * s.saadatmand@uq.edu.au is characterized by long-range dimer order and is twofold degenerate.…”