A Preisach analysis of remanence isotherms for nanoparticles of Fe in alumina

Measurements of the field and temperature dependence of the field cooled moment, the zero field cooled moment, the isothermal remanent moment (IRM), and the thermoremanent moment (TRM), are presented for a thin film of nanodimensional particles of Fe embedded in alumina ([Al.sub.2][O.sub.3]). At each measurement temperature, the TRM approaches saturation much more rapidly than the corresponding IRM, and warming accelerates the approach to saturation for both TRM and IRM isotherms. Comparisons of numerical simulations of the IRM and TRM, based on the Preisach formalism, which decomposes the metastable state excitation spectrum into an ensemble of double wells with dissipation fields Ha and bias fields [H.sub.s], with the measured isotherms, yields the distribution of characteristic fields p([H.sub.d], [H.sub.s]) and its variation with temperature. Index Terms--Hysteresis, nanoparticles, Preisach models.