TEMPERATURE-DEPENDENCE OF MAGNETOCRYSTALLINE ANISOTROPY FOR SN SUBSTITUTED BA FERRITE PARTICLES

Temperature dependence of magnetocrystalline anisotropy was measured for Co-Ti-Sn substituted Ba ferrite particles, in order to clarify the origin of a small temperature dependence of coercivity (dHc/dT) for this material. For comparison, the same measurement was carried out for Co-Ti substituted particles which have positive dHc/dT near room temperature. First and second anisotropy constants K1 and K2 were found to be both positive for these materials. The result shows they have magnetization easy directions along the c-axes. In the Co-Ti-Sn particles. K1 was dominant over K2 over the whole temperature range, and K1 decreased rapidly with increasing temperature. The rapid decrease in K1 explains the experimental small dHc/dT. In the case of Co Ti particles, K2 is not negligible below 0-degrees-C. The decrease in Hc with increasing temperature for the Co-Ti particles at a low temperature range is due to the decrease in K2. The predicted temperature dependencies of Hc derived by using the K1 and K2 values for the two kinds of materials well explain the experimental results.