FeCo基纳米晶合金高温交换耦合作用机理

研究了500和600℃真空退火后的纳米晶Fe_38.4Co₄₀Si₉B₉Nb_2.6Cu合金初始磁导率随温度的变化规律,发现较高温度(600℃)退火的FeCo基纳米晶合金,在非晶相居里温度以上较宽温度范围内磁导率没有明显的衰减,这是在双相纳米晶合金中观察到的一种新现象,其磁特性不同于Fe基纳米晶合金.为了探明这种现象的起源,估算了与剩余非晶相同成分的非晶合金的居里温度及纳米晶粒间发生交换耦合作用的参数关键词：交换耦合作用非晶相居里温度交换耦合穿透深度

Mechanism of high-temperature exchange-coupling interaction of FeCo-based nanocrystalline alloy

Temperature dependence of initial permeability is investigated for nanocrystalline Fe_38.4Co₄₀Si₉B₉Nb_2.6Cu alloy annealed at 500 and 600℃,and the initial permeability of 600℃-annealed sample is observed not to drop sharply at the Curie temperature of the residual amorphous phase,which is a new magnetic phenomenon in dual-phase nanocrystalline alloys. The origin of the above phenomenon is explored by estimating the Curie temperature of amorphous ribbons which have the same compositions with the residual amorphous phase in annealed nanocrystalline alloys. The results indicate that the Curie temperature of the intergranular amorphous region can be enhanced drastically up to the Curie temperature of the crystalline phase (T^A_C=T^α_C) when the exchange-field between adjacent nanograins penetrates through the amorphous interphase thoroughly. Furthermore, the effective exchange penetration length of FeCo-based nanocrystalline alloys (L_FeCo) is evaluated to be 0.61 nm much larger than that of Fe-based nanocrystalline alloys, which may be the main reason of the higher permeability of FeCo-based alloys at elevated temperature.