Interpreting remanence isotherms: a Preisach-based study

Numerical simulations of the field dependence of the isothermal remanent moment (IRM) and the thermoremanent moment (TRM) are presented, based on a Preisach formalism which decomposes the free energy landscape into an ensemble of thermally activated, temperature dependent; double well sub-systems. each characterized by a dissipation field H-d and a bias field H-s. The simulations show that the TRM approaches saturation much more rapidly than the corresponding IRM and that, as a consequence, the characteristics of the IRM are determined primarily by the distribution of dissipation fields, as defined by the mean field (H) over bar (d)(T) and the dispersion sigma(d)(T); while the characteristics of the TRM are determined primarily by a mixture of the mean dissipation field (H) over bar (d)(T) and the dispersion of bias fields sigma(s)(T). The simulations also identify a regime (H) over bar (d) much greater than sigma(s), where the influence of (H) over bar (d)(T) on the TRM is negligible, and hence where the TRM and the IRM provide essentially independent scans of the Preisach distribution along the two orthogonal H-s and H-d directions, respectively. The systematics established by the model simulations are exploited to analyze TRM and IRM data from a mixed ferromagnetic perovskite Ca0.4Sr0.6RuO3, and to reconstruct the distribution of characteristic fields H-d and H-s, and its variation with temperature.