Thermally Activated Domain Wall Movement in Nickel‐Iron Films

The slow movement of domain walls under a steady field, due to thermal activation, has been observed in a permalloy film, and a quantitative study made over the temperature range ‐39 to +77 °C. Unlike results obtained previously in another film [8], these do not conform to the simple theory. The theory is extended to include switching by a sinusoidal field, and the ac coercivities are correlated with the dc results. It is suggested that magnetic viscosity should be more pronounced in films with high magnetization dispersions. Some criticisms of the simple theory are advanced. An estimate of the frequency factor C is made from the results on both films, which is higher than theoretical predictions.