Local spin resonance and spin-Peierls-like phase transition in a geometrically frustrated antiferromagnet

TL;DR

This study reveals a localized spin resonance in a frustrated antiferromagnet that emerges abruptly at a phase transition, resembling a three-dimensional spin-Peierls transition, as observed via neutron scattering.

Contribution

It reports the discovery of a spin resonance and a phase transition in ZnCr2O4, proposing a new analogy to the spin-Peierls transition in three dimensions.

Findings

Localized spin resonance at 4.5 meV in ZnCr2O4

Abrupt development of resonance at T_c=12.5 K

First-order transition to a co-planar antiferromagnet

Abstract

Using inelastic magnetic neutron scattering we have discovered a localized spin resonance at 4.5 meV in the ordered phase of the geometrically frustrated cubic antiferromagnet $\rm ZnCr_2O_4$. The resonance develops abruptly from quantum critical fluctuations upon cooling through a first order transition to a co-planar antiferromagnet at $T_c=12.5(5)$ K. We argue that this transition is a three dimensional analogue of the spin-Peierls transition.