Magnetocrystalline anisotropy of single crystals of M-, X-, and W-type strontium hexaferrites

We have grown single crystals of non-substituted M-, X-, and W-type strontium hexaferrites by utilizing the traveling solvent floating zone technique and investigated their magnetic and electrical properties. Their saturation moments at 5 K are in good agreement with Gorter's model, which predicts saturation moments of 20, 24, and 28 μ_B, respectively. Owing to low thermal demagnetization, the W-type ferrite has the largest saturation moment per unit mass at room temperature. While the anisotropy fields of the M- and X-type ferrites are almost temperature-independent, that of the W-type ferrite markedly decreases below approximately 100 K. This decrease is closely related to the localization of Fe²⁺, which is suggested by the enhanced electrical resistivity at low temperatures.(author)