Mechanism of improved high-temperature magnetic softness for Co-contained Finemet alloy

摘要

Herein, the temperature dependence of initial permeability was investigated for nanocrystalline (FeCo)SiBNbCu alloy annealed at 530 and 660. It has been observed that the initial permeability of 530-annealed sample gradually droped to zero at 425 (the Curie temperature of as-quenched amorphous alloy), however the initial permeability of 660-annealed sample did not drop to zero at 425, which is a new magnetic phenomenon in two-phase nanocrystalline alloys. The origin of the phenomenon has been analyzed by estimating the Curie temperature of as-quenched amorphous alloy,T, which has the same composition with the residual amorphous phase in annealed nanocrystalline alloy as well as the Curie temperature of the intergranular amorphous region T. The results indicated that the T did not enhanced after nanocrystallization, however the Curie temperature of intergranular amorphous region T can be elevated drastically up to the Curie temperature of crystalline phase (T =T) when the exchange-field between adjacent nanograins penetrated the amorphous interphase thoroughly. Furthermore the effective exchange penetration length of Co-contained Finemet alloy (LFeCo) was evaluated, which is about 0.61nm, larger than that of Finemet alloys.