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

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, T^system_c and T^cluster_c. T^cluster_c is the Curie temperature of the magnetic clusters, which is also the Curie temperature of the sample. T^system_c is the measurement of the strength of interactions between clusters. Between T^cluster_c and T^system_c, the system exhibits superparamagnetism with strong cluster interactions. The strong cluster interactions result in the ferromagnetic state below the critical temperature (T^system_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 T_block and T^system_c are also discussed in this article.