FMR study of surface and isothermal annealing effects in amorphous Fe₈₀B_20-xC_x and Fe₈₂B_18-yGe_y alloys

Abstract

Alterations in the bulk (surface) magnetic properties of amorphous Fe₈₀B_20-x C_x (0 ≤ x ≤10) and Fe₈₂ B_18-y Ge_y (0 ≤ y ≤ 6) alloys, caused by isothermal annealing (mechanical polishing) of the alloy ribbons at a temperature T_A= 0.5T_cr (whereT_cr is the crystallization temperature) for various lengths of time,t_a, ranging from 0 to 240 min, have been studied by measuring the corresponding changes in the ferromagnetic resonance (FMR) linewidth, ΔH_PP, and resonance field, H_res. Polishing induces significant changes in bothH res and ΔH_pp but leaves their composition dependence practically unaltered. By comparison, isothermal annealing has no influence on H_res for all the investigated alloy compositions whereas it affects ΔH_pp to different extents depending on the alloy composition. Physical implications of these results are discussed in terms of the effect of surface and annealing treatments on various contributions to H_res and ΔH_pp in the glassy alloys in question.