A new model for the acquisition of thermoremanence by multidomain magnetite

Isothermal remanence (IRM) induced in multidomain grains at high temperature (T_i) decreases on cooling in zero field. The intensity and stability (against temperature change) of the IRM depend on whether the temperature (T_i) was reached from higher temperature or from lower temperature. These results cannot be explained by the existing multidomain theories. A new model of a thermoremanence (TRM) acquisition mechanism, in which domain wall interactions play the major role, is proposed. This model explains the main features of the experimental results very well, predicting an almost linear relationship between TRM and the inducing field, up to relatively high fields.