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.
Categories: cond-mat.mtrl-sci
