Evidence for orthorhombic distortions in the ordered state of ZnCr$_2$O$_4$: A magnetic resonance study

TL;DR

This study uses electron-spin resonance to reveal orthorhombic distortions in the ordered phase of ZnCr₂O₄, showing how magnetic domains can be manipulated and highlighting the importance of lattice distortions in understanding its magnetic properties.

Contribution

It provides evidence for orthorhombic distortions in ZnCr₂O₄'s ordered state, extending previous models that only considered tetragonal distortions.

Findings

Multiple resonance modes indicate different structural domains.

Field-cooling reduces the number of magnetic domains.

Orthorhombic distortion is necessary to explain the resonance spectra.

Abstract

We present an elaborate electron-spin resonance study of the low-energy dynamics and magnetization in the ordered phase of the magnetically frustrated spinel ZnCr$_2$O$_4$. We observe several resonance modes corresponding to different structural domains and found that the number of domains can be easily reduced by field-cooling the sample through the transition point. To describe the observed antiferromagnetic resonance spectra it is necessary to take into account an orthorhombic lattice distortion in addition to the earlier reported tetragonal distortion which both appear at the antiferromagnetic phase transition.