Zero-field relaxation and exchange interactions in magnetic thin films - art. no. 020401

A zero-field relaxation phenomenon has been observed and studied in a serie s of CoPtCrB thin-film samples with progressively decreasing grain size. In particular, a nonmonotonic time dependence of the magnetization has been m easured in zero external magnetic field after partial de demagnetization of the samples. The zero-field relaxation rate becomes increasingly strong as grain sizes approach the superparamagnetic limit. The phenomenon is ascrib ed to a cooperative influence of intergranular interactions and thermal eff ects and is described using an extended Preisach-type model that includes t hermal relaxation effects.