Crystal-field-induced magnetostrictions in the spin reorientation process of Nd$_2$Fe$_{14}$B-type compounds

TL;DR

This paper investigates how crystal field effects induce volume changes during spin reorientation in Nd$_2$Fe$_{14}$B compounds, linking volume expansion directly to second order crystal-electric-field energy and reproducing observed anomalies.

Contribution

It introduces a simple CEF model to quantitatively relate volume expansion to spin reorientation and reproduces experimental anomalies in Nd$_2$Fe$_{14}$B.

Findings

Volume expansion correlates with second order CEF energy.

Calculated anomalies match experimental observations.

Volume change serves as a measure of CEF effects.

Abstract

Volume expansion $\Delta V / V$ associated with the spin reorientation process of Nd$_2$Fe$_{14}$B-type compounds has been investigated in terms of simple crystalline-electric-field (CEF) model. In this system, $\Delta V / V$ is shown to be a direct measure of second order CEF energy. Calculated anomalies in $\Delta V / V$ associated with the first-order magnetization process of Nd$_2$Fe$_{14}$B are presented, which well reproduced the observations.