Magnetic excitations in dipolar pyrochlore antiferromagnet Gd$_2$Sn$_2$O$_7$

TL;DR

This study investigates the spin dynamics of the dipolar pyrochlore antiferromagnet Gd2Sn2O7 using electron spin resonance, revealing three gapped modes consistent with spin-wave theory and predicting a fourth mode affecting low-temperature specific heat.

Contribution

The paper provides experimental ESR data and confirms a spin-wave theoretical model that includes exchange, anisotropy, and dipolar interactions in Gd2Sn2O7.

Findings

Detected three gapped resonance modes in the ordered phase.

The resonance modes agree with the developed spin-wave theory.

Predicted a fourth mode influencing low-temperature specific heat.

Abstract

The spin dynamics in the geometrically frustrated pyrochlore antiferromagnet $\rm Gd_2Sn_2O_7$ is studied by means of the electron spin resonance. In the ordered phase ($T_N = 1$ K), 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 of the specific heat at low temperature.