A survey of the magnetization reversal for CoCr films and some particulate recording media

In addition to previous research on the magnetization reversal for sputtered CoCr films, two particulate perpendicular recording media, namely Ba-ferrite and Alumite have been measured. For comparison an isotropic Ba-ferrite sample and an in-plane g Fe2O3 magnetic tape have also been evaluated. Only a few properties are compared which have been determined from the field- and angle-dependent VSM measurements. It was discovered for high Hc/Hk CoCr films and the orientated Ba-ferrite media, in which the perpendicular anisotropy mainly results from crystalline anisotropy, that the magnetization reversal is mainly controlled by a Cos-type of incoherent rotation. On the other hand, for a magnetic tape having a high longitudinal orientation ratio, the magnetization reversal is determined by the curling-type of incoherent rotation. The isotropic Ba-ferrite media exhibit rather good in-plane characteristics. For Alumite (an array of Fe needles) it was found that the measured reduced coercivity vs. reduced diameter fit very well with the theoretical curling mode. But if the applied field deviates from the film normal, the magnetization reversal can be interpreted rom the superposition of Cos-type of incoherent rotation and a contribution from the demagnetizing field and dipole-dipole field.