An analysis of the high-temperature initial susceptibility of single-crystal cobalt

The ac initial susceptibility of a cobalt single crystal with [0001] orientation has been measured in the temperature range 300 to 820 K. A theoretical treatment of the susceptibility in the range 300 to 700 K has been given in terms of the contributions of domain wall displacements and magnetization vector rotations in the appropriate temperature intervals; this theoretical treatment is found to be in good agreement with the experimentally observed variation. Measurements in the range 700 to 820 K include the martensitic phase transformation at 710 K, which has a pronounced influence on the susceptibility. Magnetic relaxation measurements have also been made over the whole temperature range (300 to 820 K) and are found to be fully consistent with the interpretation of the susceptibility data. An important feature of the relaxation spectrum is a null region (584 to 710 K) which corresponds to that temperature range where contributions to the susceptibility occur due solely to magnetization rotations.