Magnetostriction of Erbium Single Crystals

The magnetostriction of Er single crystals has been measured from 300 to 10°K in applied fields up to 30 kOe. In contrast to the other rare earths, the magnetostriction of Er is dominated by field-induced modifications of the exchange energy. The exchange magnetostriction which results from the application of a $c$-axis field has been determined in the quasi-antiphase-domain and modulated-moment temperature regions. Below 20°K, application of a field in the basal plane produced a sharp change in strain at 18 kOe. This is presumed to arise from a breakdown of the conical ferromagnetic structure into a conical fan state. The second-order anisotropic basal-plane magnetostriction constant was measured. Negative values were found above 55°K in accordance with theoretical predictions. Below 18°K anomalously small and positive values were obtained. The temperature dependence of the $a$-, $b$-, and $c$-axis strains in zero field and in a 30-kOe field was evaluated.