Observation of gyromagnetic reversal

TL;DR

This study directly observed gyromagnetic reversal in a ferrimagnet using the Barnett effect, revealing temperature-dependent sign changes of the gyromagnetic ratio and providing a new method to explore gyromagnetic properties.

Contribution

It demonstrates the first direct measurement of gyromagnetic reversal in Ho$_3$Fe$_5$O$_{12}$ using the Barnett effect at low temperatures, linking it to magnetization and angular momentum compensation points.

Findings

Gyromagnetic ratio changes sign at specific temperatures.

Magnetization induced by rotation disappears at two characteristic temperatures.

Reversal of magnetization direction occurs between these temperatures.

Abstract

We report direct observation of gyromagnetic reversal, which is the sign change of gyromagnetic ratio in a ferrimagnet Ho$_3$Fe$_5$O$_{12}$, by using the Barnett effect measurement technique at low temperatures. The Barnett effect is a phenomenon in which magnetization is induced by mechanical rotation through the coupling between rotation and total angular momentum $J$ of electrons. The magnetization of Ho$_3$Fe$_5$O$_{12}$ induced by mechanical rotation disappears at 135~K and 240~K. The temperatures correspond to the magnetization compensation temperature $T_{\rm M}$ and the angular momentum compensation temperature $T_{\rm A}$, respectively. Between $T_{\rm M}$ and $T_{\rm A}$, the magnetization flips over to be parallel against the angular momentum due to the sign change of gyromagnetic ratio. This study provides an unprecedented technique to explore the gyromagnetic properties.