Effects of magnetostatic interaction on the magnetization processes in Fe_73.5Cu₁Nb₃Si_13.5B₉ nanocrystalline wires

Fe_73.5Cu₁Nb₃Si_13.5B₉ amorphous wire was annealed at different temperatures (T_a = 400-700C°, for 30 min) that result in partial devitrification and subsequently, the quasi-saturated hysteresis loop was measured. It is found that the loops are not symmetric, exhibiting two coercive fields, H_c1 and H_c2, on descending and ascending branches, respectively. Moreover, the asymmetry degree is modified when the sample is previously magnetized under a field of 60 kA m^-1. The dependence on both maximum measured field, H_m, and temperature, T, of the displaced loop has been determined. With increasing H_m, the shift H_sh = (H_c2 + H_c1)/2 decreases and the coercivity H_c = (H_c2-H_c1)/2 increases, but H_sh-H_c = H_c1 remains constant. Both H_sh and the magnetic polarization, µ₀M_m, at maximum field decreases with elevating T. The loop of this sample also shows a remarkable time-effect. The H_m- and T-dependent H_sh is discussed considering the existence of an effective bias-field generated from the magnetostatic interaction between the nanocrystalline particles and residual soft matrix, and the time-effect could be ascribed to the dipolar interaction among the particles.