Curie temperatures for amorphous TM 100− XGd X(TM ≡ Fe, Co; 40 ⩽ X ⩽ 60) alloys

Abstract

The Curie temperatures T c for melt-spun amorphous TM 100− X Gd X (TM ≡ Fe, Co; 40 ⩽ X ⩽ 60) alloys have been investigated with the aid of molecular field theory. The values of T c are determined experimentally from both Arrott plots and the temperature dependence of the magnetization at low magnetic field. In addition, Arrott plots are calculated in terms of molecular field theory with three fitting parameters derived from the fitting of M( T) curves. Experimental results by both methods are nearly identical. The Arrott plots in the Gd-rich region ( X > 50) for the FeGd system show clear deviations from a linear relationship around T c and are conspicuously different from those for the CoGd system, where the Arrott plots are normally linear. Considering the results that the calculated Arrott plots reproduce the deviations qualitatively, it can be concluded that the curvatures in the Arrott plots for amorphous Fe 100− X Gd X alloys ( X > 50) are intrinsic and both experimental methods are capable of determining the Curie temperatures.