Magnetization process and torque curves in HCP cobalt

Magnetization measurements were made in HCP cobalt by using a very-low-frequency vibrating sample magnetometer in the same external field range where torque curve analyses were performed. The anomalously small value of K_u1 analyzed from the torque curves in the very low field region below 0.3 T was found to be attributable to the appearance of a multiple-domain configuration. If one excludes the multiple-domain configuration range in analyzing observed torque curves, it becomes possible to determine precisely the magnetocrystalline anisotropy constants. The applicability of least-mean-square analysis to unsaturated torque curves is confirmed within the range where the single-domain configuration occurs