Magnetic excitations in the spin-1/2 triangular-lattice antiferromagnet Cs2CuBr4

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, ${\rm{\Delta }}\approx 9.5$ K, observed in the low-temperature excitation spectrum of Cs _2 CuBr _4 , (Zvyagin et al 2014 Phys. Rev. Lett. http://dx.doi.org/10.1103/PhysRevLett.112.077206 112 http://dx.doi.org/10.1103/PhysRevLett.112.077206 ) 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 triangular-lattice antiferromagnet.

Keywords

• magnetism
• frustration
• spectroscopy
• 75.40.Gb
• 76.30.-v
• 75.10.Jm