Magnetic properties of Tb 1− xY x(Co 0.85Si 0.15) 2 compounds

Abstract

A series of Tb 1− x Y x (Co 0.85Si 0.15) 2 compounds was prepared for x=0, 0.2, 0.4, 0.6, and 0.8. The Curie temperatures were determined by AC susceptibility measurements and the temperature dependence of the magnetisation was measured in an applied field of 0.2 T. Magnetisation curves were determined at 4.2 K in applied fields up to 10 T. In the curves obtained for the compounds with x<0.8, a clear hysteresis was found at low fields (up to 2 T) and at moderate fields (2–8 T). The anomaly at lower fields is ascribed to freezing-in phenomena and domain wall pinning. The same effects may cause the observed splitting of field-cooled and zero-field-cooled magnetisation vs. temperature curves in an applied field of 30 mT. The behaviour of the anomaly at moderate fields as a function of the Tb concentration is discussed in a two-subsystem molecular-field model. The anomaly is tentatively ascribed to a metamagnetic transition in the Tb subsystem.