Thermal relaxation of magnetic clusters in amorphous Hf_{57}Fe_{43} alloy

TL;DR

This study investigates the magnetic relaxation phenomena in amorphous Hf_{57}Fe_{43} alloy, revealing superparamagnetic behavior of magnetic clusters and their thermal relaxation dynamics.

Contribution

It provides detailed analysis of magnetic relaxation and cluster sizes in amorphous Hf_{57}Fe_{43}, supporting the superparamagnetic model for this alloy.

Findings

Magnetic clusters range from 25 to 200 nm^3 in volume.

Magnetic relaxation is governed by thermal fluctuations over anisotropy barriers.

Superparamagnetic behavior explains the magnetic properties of the alloy.

Abstract

The magnetization processes in binary magnetic/nonmagnetic amorphous alloy Hf_{57}Fe_{43} are investigated by the detailed measurements of magnetic hysteresis loops, temperature dependence of magnetization, relaxation of magnetization and magnetic ac susceptibility, including a nonlinear term. Blocking of magnetic moments at lower temperatures is accompanied with the slow relaxation of magnetization and magnetic hysteresis loops. All of the observed properties are explained with the superparamagnetic behaviour of the single domain magnetic clusters inside the nonmagnetic host, their blocking by the anisotropy barriers and thermal fluctuation over the barriers accompanied by relaxation of magnetization. From magnetic viscosity analysis based on thermal relaxation over the anisotropy barriers it is found out that magnetic clusters occupy the characteristic volume from 25 up to 200 nm3 . The validity of the superparamagnetic model of Hf_{57}Fe_{43} is based on the concentration of iron in the Hf_{100-x}Fe_{43} system that is just below the threshold for the long range magnetic ordering. This work throws more light on magnetic behaviour of other amorphous alloys, too.