Magnetocrystalline Anisotropy of Single-Crystal Europium Oxide

The first-order cubic anisotropy constant $K_1$ in EuO single crystal was measured as a function of temperature and applied field by the static torque method. The value at $T=0\mathrm{}°$K is $K_1\mathrm{}\left(0\right)=-(4.36\mathrm{}\pm 0.1)\times {10}^5$ erg/${\mathrm{cm}}^3$. The variation of $K_1$ with $T$ and $H$ is uniquely described by the behavior of the measured magnetic moment $\sigma (H, T)$. The observed relationship between $\frac{K_1(H, T)}{K_1(0, 0)}$ and $\frac{\sigma (H, T)}{\sigma (0, 0)}$ is explained by a theory of single-ion interaction with the cubic crystal potential. The cubic crystal-field splitting parameter $b_4=(21.2\mathrm{}\pm 0.5)\times {10}^{-4\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$/ion obtained from $K_1\mathrm{}\left(0\right)\mathrm{}$ is compared with results for ${\mathrm{Eu}}^{++}$ ions in various other materials.