A Preisach analysis of a reentrant ferromagnet Fe0.65Ni0.23Cr0.12

Measurements of the initial magnetizing curve, the magnetizing remanence, t he descending branch of the major hysteresis loop, and the demagnetizing re manence have been performed on a reentrant ferromagnet Fe0.65Ni0.23Cr0.12, at several temperatures in the vicinity of the postulated ferromagnetic-spi n glass "reentrant transition." Henkel plots of the principal magnetizing a nd demagnetizing remanences show a systematic change in curvature with temp erature, from a "high temperature" regime T greater than or equal to 8 K wh ere the curvature is predominantly magnetizing-like to a "low temperature" regime T less than or equal to 6 K where the curvature is purely demagnetiz ing-like. Numerical simulations based on a Preisach model which includes th ermal fluctuations show that this behavior is consistent with a physical pi cture of coupled bistable subsystems with a temperature dependent distribut ion of interaction fields, which evolves with decreasing temperature from a regime dominated by long range ferromagnetic interactions to a regime in w hich the interaction fields fluctuate randomly about a zero mean. (C) 2000 American Institute of Physics. [S0021- 8979(00)15308-3].