Dynamic-thermal effects in thin film media

Thermal dynamic effects are discussed for both short write times and long storage times in thin film media. A new analytic model for coercivity versus pulse time for the entire time range is presented for planar random media. Neel-Arrhenius analysis is shown to be accurate only for times greater than about 100-1000 nsec. The effective volume in the long time Neel-Arrhenius regime is the rms volume for a distribution of grain sizes. For planar random media the volume is increased about 7% and is independent of intergranular interactions. The presence of a small K-2 hexagonal anisotropy in typical Co based alloys increases the stability, but has less effect on the intrinsic reversal field and the short time dynamic writing field. Increasing the damping constant may significantly reduce the write field, but, for both longitudinal and perpendicular media, yields only a very small increase in the thermal decay. Analysis of short time write fields in terms of a "switching constant" is shown not to be fundamental to these hard materials.