Magnetic analysis of rapidly quenched LaFe alloys-a ferromagnetically coupled ferromagnetic cluster system: II. Analysis of the magnetization of as-quenched alloys

The magnetization of rapidly quenched LaFe alloys with < 12 at.% Fe, reported in Part I, was analysed. The alloy can be considered as a random set of ferromagnetic clusters with inter-cluster ferromagnetic coupling. It was demonstrated that the magnetization of an alloy for different external fields and temperatures can be expressed as a function of either H/(T-T sub C exp inter ) in the super-paramagnetic region (290 < = T < = 380K) or (H + omega M)/T in a slightly wider temperature range (240 < = T < = 380K), provided that the temperature dependence of the magnetization of a cluster is taken into account. Here, T sub C exp inter is the asymptotic Curie temperature and omega is the molecular-field constant for the inter-cluster coupling. The relations gave estimates of the average cluster size, 100-1500 Fe atoms, which depends not on the iron concentration but on the quenching process. Magnetization in the ferromagnetic region, 5 < T < 250K, was analysed by the use of the molecular-field approximation with distributed cluster size and exchange coupling constant.