TEMPERATURE DEPENDENCE OF THE MAGNETIC VISCOSITY IN CoCrTa AND CoCrPtTa THIN FILMS

The temperature dependence of the magnetic viscosity coefficient (Sv), the activation volume (Vact) and the coercivity (Hc) were examined for CoCrTa/Cr and CoCrPtTa/Cr thin films in the temperature range from 200 to 423 K. This experiment shows that the medium noise measured for 150 kFCI is approximately proportional to kT/Sv (=Vact × Ms) at 298K. kT/Sv and the temperature variation of coercivity (dHc/dT) increase with increasing temperature. The relationship, HA/50Sv > 1 was obtained from the thermal stability of magnetization, where HA is the anisotropy field. However, in practice one must compare Hc instead of HA with 50Sv. The factor Hc/50Sv, a measure of the thermal stability of the magnetization, was close to 1.3 -1.7 at 373 K.