Temperature dependence of the time decay of the magnetization in particulate media

We have studied the temperature dependence of the time decay of the magnetization, dM/d lnt, in magnetic tapes as a function of reversal magnetic field, following an initial applied saturating field. We find the maximum decay rate occurs at the coercive field for all temperatures from 300 down to 6 K. Theoretical results and the available experimental data for studies in rock magnetism and ferromagnetic materials suggest the maximum magnetization decay should be proportional to the temperature. While we do find a linear temperature dependence, the data do not extrapolate to zero at T = 0 K, but surprisingly imply a finite value.