Magnetic aftereffect in CoCr films

We have studied the relaxation or decay of the perpendicular remanent magnetization of CoCr films after the removal of a saturating magnetic field. The films have a perpendicular anisotropy and are similar to those being studied for application as perpendicular recording media. The time dependence of the decay of the magnetization was determined by measuring the magnitude of the magnetization continuously for time periods up to a thousand minutes using a SQUID magnetometer. This time dependence was studied over a range of temperatures for each of the samples (10-300 K). The decays are found to be quasilogarithmic over at least three decades of time and have been compared to two phenomological models. A fit to one model's decay rate indicates the temperature dependence of the decay rate is nonmonotonic, i.e., the decay rate is a maximum in an intermediate temperature region for the films we have studied.