Abstract
The spin dynamics in the geometrically frustrated pyrochlore antiferromagnet is studied by means of the electron spin resonance. In the ordered phase , we have detected three gapped resonance modes. Their values agree well with the developed spin-wave theory which takes into account the Heisenberg nearest-neighbor exchange, the single-ion anisotropy, and the long-range dipolar interactions. The theory also predicts a fourth lowest-frequency gap, which lies beyond the experimental range of frequencies, but determines the exponential decrease in the specific heat at low temperature.
- Received 4 September 2008
DOI:https://doi.org/10.1103/PhysRevB.79.014419
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