The irreversible relaxation of magnetization and curie temperature in amorphous Co-P and Fe-P alloys

Abstract

Irreversible structural relaxation in amorphous Fe-P and Co-P is accompanied by a small reduction of the saturation magnetization σ 0 of about 1%. Simultaneously the Curie temperature of Fe-P increases by at least 3 K independent of composition. The main contribution to the drop of σ 0 should come from the strengthening of the chemical bonds between metalloid and metal atoms as a consequence of a diffusionless rearrangement, but the influence of chemical decomposition must not be neglected. Decomposition does not cause the changes in T c because the Curie temperature of Fe-P is nearly independent of the phosphorus content. The shift of T c has probably to do with the pronounced irreversible densification of Fe-P upon annealing and a corresponding enhancement of the Fe-Fe correlation. The corresponding results obtained on Co-P fit to this picture though in this case the experimental resolution is insufficient to determine a change of T c smaller than 8 K.