Transition to superparamagnetism in a Cr-containing FINEMET-type alloy

The transition from a ferromagnetic to a superparamagnetic regime has been studied in a Cr-containing FINEMET-type alloy. Cr enhances the thermal stability of the alloy against nanocrystallization and reduces the Curie temperature of the remaining amorphous phase. Above room temperature, the temperature dependent hysteresis loop of a nanocrystalline sample can be described by a model of interacting superparamagnetic particles. The temperature dependence of the apparent magnetic moment of the particles obtained from the fittings is interpreted in an extended version of the model. Index Terms--Hysteresis, magnetic materials, magnetization processes.