Magnetic excitations in the spin-1/2 triangular-lattice antiferromagnet Cs${}_2$CuBr${}_4$

Abstract

We report on high-field electron spin resonance (ESR) studies of magnetic excitations in the spin-1/2 triangular-lattice antiferromagnet Cs${}_2$CuBr${}_4$. Frequency-field diagrams of ESR excitations are measured for different orientations of magnetic fields up to 25 T. We show that the substantial zero-field energy gap, $\Delta \approx 9.5$ K, observed in the low-temperature excitation spectrum of Cs${}_2$CuBr${}_4$ [Zvyagin $etal.$, Phys. Rev. Lett. 112, 077206 (2014)], is present well above $T_N$. Noticeably, the transition into the long-range magnetically ordered phase does not significantly affect the size of the gap, suggesting that even below $T_N$ the high-energy spin dynamics in Cs${}_2$CuBr${}_4$ is determined by short-range-order spin correlations. The experimental data are compared with results of model spin-wave-theory calculations for spin-1/2 triangle-lattice antiferromagnet.

6 pages, 9 figures

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• Spontaneous Magnon Decays
• Spinons and triplons in spatially anisotropic frustrated antiferromagnets
• Excitation spectra of the spin-1/2 triangular-lattice Heisenberg antiferromagnet
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• Spin Structure Factor of the Frustrated Quantum Magnet Cs_2CuCl_4
• Magnetic resonance in the ordered phases of the 2D frustrated quantum magnet Cs2CuCl4
• Quasiparticles of spatially anisotropic triangular antiferromagnets in a magnetic field
• High-field spectroscopy of singlet-triplet transitions in the spin-dimer systems Sr3Cr2O8 and Ba3Cr2O8

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• Spin relaxation in Cs${}_2$CuCl${}_{4-x}$Br${}_x$
• Anomalous magnetic exchange in a dimerized quantum-magnet composed of unlike spin species