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arXiv · 2309.02266

Dynamics of anisotropic frustrated antiferromagnet Cs2CoBr4 in a spin-liquid regime

T. A. Soldatov·A. I. Smirnov·A. V. Syromyatnikov
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Abstract

Cs2CoBr4 is a triangular-lattice antiferromagnet which can be viewed as weakly interacting spin chains due to spatially anisotropic frustrating exchange couplings. The spin-orbit interaction in Co(2+) spin-3/2 ions leads to a strong easy-plane single-ion anisotropy which allows to consider the low-energy spin dynamics of this system using an anisotropic pseudospin-1/2 model. By means of the electron spin resonance (ESR) technique, we study the spin dynamics of Cs2CoBr4 in magnetic field in a spin-liquid regime, i.e., above the N'eel temperature of 1.3 K but below the temperature of the crossover to in-chain correlations of pseudospins (6 K). Our experiments reveal two bright branches of excitations which strongly differ both from excitations in the low-temperature ordered phases and from high-temperature paramagnetic resonance of uncorrelated pseudospins and spins. These two branches are interpreted as excitations with zero momentum of an anisotropic spin-1/2 chain. Besides, we observe several weak modes of unknown origin which arise mostly as satellites of one of the bright modes.

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T. A. Soldatov, A. I. Smirnov, A. V. Syromyatnikov. 2023-09-05. Dynamics of anisotropic frustrated antiferromagnet Cs2CoBr4 in a spin-liquid regime. https://arxiv.org/abs/2309.02266

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