Model of ferromagnetic clusters in amorphous rare earth and transition metal alloys

Abstract

Experimental results on amorphous rare earth and transition metal alloys suggest the presence of Fe-rich clusters. A model is proposed in which the magnetic units are magnetic clusters. The magnetization of the clusters decreases with the increase of temperature. In this model, there are two critical temperatures, Tsystem c and Tcluster c. Tcluster c is the Curie temperature of the magnetic clusters, which is also the Curie temperature of the sample. Tsystem c is the measurement of the strength of interactions between clusters. Between Tcluster c and Tsystem c, the system exhibits superparamagnetism with strong cluster interactions. The strong cluster interactions result in the ferromagnetic state below the critical temperature (Tsystem c), which is called a cluster ferromagnetism. Our experimental data (magnetization curves and susceptibility values of amorphous Y60Fe30Al10 and Nd60Fe30Al10 ribbons) support the cluster ferromagnetic model. The zero temperature coercivity and the relationship between Tblock and Tsystem c are also discussed in this article. © 2001 American Institute of Physics.