Abstract
We report on high-field electron spin resonance (ESR) studies of magnetic excitations in the spin-1/2 triangular-lattice antiferromagnet Cs2CuBr4. 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, K, observed in the low-temperature excitation spectrum of Cs2CuBr4, (Zvyagin et al 2014 Phys. Rev. Lett.112 077206) is present well above TN. Noticeably, the transition into the long-range magnetically ordered phase does not significantly affect the size of the gap, suggesting that even below TN the high-energy spin dynamics in Cs2CuBr4 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.
Highlights
The frequency-field diagram of magnetic excitations in Cs2CuBr4 measured between 0.4 and 4 K for magnetic fields, H, applied along the b-axis is shown in figure 1
Some examples of electron spin resonance (ESR) spectra of magnetic excitations at different frequencies are presented in figure 2
The temperature dependence of the ESR field position at a frequency of 295.2 GHz with magnetic field applied along the b-axis is shown in figure 3 by squares
Summary
The frequency-field diagram of magnetic excitations in Cs2CuBr4 measured between 0.4 and 4 K for magnetic fields, H, applied along the b-axis is shown in figure 1. Electron spin resonance (ESR) studies provided additional support for the proposed quasi-1D Heisenberg AF chain model with the uniform Dzyaloshinskii–Moriya (DM) interaction, opening an energy gap, D = 14 GHz, at the Γ point [16]. Similar effects were observed in a number of quantum AFs [24,25,26,27], whose ground states below TN are 3D magnetically ordered and the low-energy excitation spectra are determined by 3D long-range-order correlations, while the high-energy (~J ) spin dynamics is still determined by low-D effects.
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