Reversal field versus pulse time: Theoretical and experimental comparison

A new model of reversal field versus pulse time is used to analyze measurem ents on elongated particles in magnetic tape. The model applies to all time s and temperatures and fits the data extremely well. At long times the mode l agrees with simple N\'{e}el-Arrhenius models, but for times less than abo ut 0.1 ms exhibits a progressively increasing switching field. This increas e is shown to be due initially to a field dependent attempt frequency. At e xtremely short times dynamic processes dominate and in this regime the best estimate of the damping constant is obtained. The model gives values of ef fective volume and anisotropy that are in agrement with nonuniform reversal in these particles.