Superparamagnetic behaviour of amorphous Hf57Fe43 alloy

The magnetization processes in binary magnetic/nonmagnetic amorphous alloy Hf57Fe43 are investigated by the detailed measurements including magnetic hysteresis loops, dependence of magnetic moment on temperature and relaxation of magnetic moment. The blocking of magnetization at lower temperatures is accompanied by the slow relaxation of magnetic moment and magnetic hysteresis loops. All of observed properties are explained by the superparamagnetic behaviour of the single domain magnetic clusters inside the nonmagnetic host. The memory effects or interaction effects between clusters or with nonmagnetic matrix were not observed. From magnetic viscosity analysis based on thermal relaxation over the anisotropy barriers it is found that magnetic clusters are of approximate characteristic size 3-7nm. The validity of the superparamagnetic model of Hf57Fe43 is based on the concentration of iron in the Hf100−xFex system that is just below the threshold for the long range magnetic ordering.