Abstract
The electron spin resonance doublet indicating the width of the two-spinon continuum in a spin- triangular lattice Heisenberg antiferromagnet was studied in high magnetic field. The doublet was found to collapse in a magnetic field of one-half of the saturation field. The collapse of the doublet occurs via vanishing of the high-frequency component in a qualitative agreement with the theoretical prediction for the chain. The field of the collapse is, however, much lower than expected for the chain. This is proposed to be due to the destruction of frustration of interchain exchange bonds in a magnetic field, which restores the 2D character of this spin system. In the saturated phase the mode with the Larmor frequency and a much weaker mode downshifted for 119 GHz are observed. The weak mode is of exchange origin; it demonstrates a positive frequency shift at heating corresponding to the repulsion of magnons in the saturated phase.
- Received 6 December 2014
- Revised 28 April 2015
DOI:https://doi.org/10.1103/PhysRevB.91.174412
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