Magnetocrystalline anisotropy of ytterbium iron garnet Yb₃Fe₅O₁₂

The anisotropy of ytterbium iron garnet and ytterbium-doped yttrium iron garnet has been measured by the torque method in applied fields of 15 000 Oe at temperatures between 1.5 °K and 300 °K. Theoretical values of the anisotropy were calculated from optical energy level data derived by other workers and these were compared with the experimental results. At temperatures below 4.2 °K, the experimental measurements of anisotropy energy showed anomalies along certain crystallographic directions and the magnitude of the effects has been measured as a function of temperature and concentration of ytterbium. Possible mechanisms to explain the occurrence of these anomalies are discussed.