A Preisach model with a temperature and time-dependent remanence maximum

We present a simple physical model which is capable of generating a maximum in the field dependence of both the isothermal remanent magnetization and the thermoremanent magnetization, with temperature and time-dependent systematics which are identical to those observed experimentally in spin glasses. The model uses an output dependent (moving) Preisach formalism to calculate the response to an applied field of a collection of interacting two-level subsystems with intrinsic anisotropy barriers, which are allowed to relax to equilibrium by thermal over-barrier activation. The maxima occur when the distribution of subsystem anisotropies has an output dependence which reduces the mean activation barrier in proportion to the magnetization induced in the system, so that the thermal relaxation processes become progressively more effective as the system approaches saturation. (C) 1997 American Institute of Physics.