Breakdown of magnetism in the amorphous alloy system (Fe_1-xNi_x)₇₇Si₁₀B₁₃

Abstract

Magnetic susceptibility and Mossbauer measurements are reported for amorphous (Fe1-xNix)77Si10B13 in a Ni concentration range 0.85<or=x<or=1, where the breakdown of magnetism occurs. The authors propose a magnetic phase diagram in which, for x<0.91, long-range magnetic order undergoes a transition to a cluster-glass state. The pronounced influence of magnetic clusters upon the temperature and field dependence of the magnetisation is reflected in strongly curved Arrott plots and gives rise to spin-wave contributions even for alloys with low Curie temperatures. The fairly high ratio of the paramagnetic moment to the spontaneous moment is discussed in terms of a recent theory by Wagner and Wohlfarth (1980).