Predicted time dependence of the switching field for magnetic materials

A scaling relationship between switching fields, of which remanent coercivity is a prominent example, and measurement time is derived. The energy barrier to thermal fluctuations is found to exhibit a (3/2-power dependence on the difference between the applied field and the nonthermally assisted switching field. This (3/2-power dependence contrasts with the 2-power dependence which has been widely assumed in the literature. Implications for magnetic viscosity and the orientational dependence of the time-dependent switching field in certain small, isolated particles are also discussed.