多场耦合Fe基合金巨磁阻抗效应调控机制

Regulation mechanism of giant magneto-impedance effect of multi-field coupling Fe-based alloy

Fe基合金性能优异,是首选的“双绿色”节能材料,在电力电子信息领域具有重要的应用价值.本文对单辊快淬制备的Fe_(64.8)Co_(7.2)Nb_(4)Si_(4.8)B_(19.2)非晶薄带实施多场耦合热处理(电流张应力退火),采用阻抗仪和磁力显微镜观测薄带纵向驱动巨磁阻抗效应及磁畴结构,结合X射线衍射、随机各向异性模型和数值拟合分析薄带的磁晶各向异性和应力各向异性,提出磁各向异性竞争因子k,从磁各向异性角度研究合金带巨磁阻抗效应调控机制.结果表明,k≤0.147的薄带展现出“单峰”和“穹顶”状的巨磁阻抗效应,且具有较规则的横向磁畴结构;而k>0.147的薄带展现出“尖刺+穹顶”状巨磁阻抗效应,同时在较不规则的横向畴畴壁处观测到新畴的形核和分裂,这为磁各向异性的竞争抑制作用提供了佐证.因此,本研究认为多场耦合热处理Fe_(64.8)Co_(7.2)Nb_(4)Si_(4.8)B_(19.2)合金薄带展现出良好的应力敏感特性可由磁各向异性的竞争抑制作用解释,它是材料巨磁阻抗效应实现调控的主要原因,在调制优化材料磁性能方面具有良好的应用前景.

Fe-based amorphous and nanocrystalline alloys are considered as the preferred dual-green energy-saving materials due to their unique magnetic properties,such as high permeability,low coercivity,and near-zero saturation magnetostriction.As such,they have received extensive attention in applications like magnetic core material for high-frequency transformers,common model chokes,ground fault interrupters,and rotors in motors,over the past decades.In this work,Fe_(64.8)Co_(7.2)Nb_(4)Si_(4.8)B_(19.2)(in atom percent)amorphous alloy ribbons are prepared by using the single roller quenching method,then subsequently subjected to multi-field coupling heating treatment in the air which includes heating by Joule heating effect and tensile stress field.Furthermore,the longitudinally driven giant magneto-impedance effect and magnetic domain structures of ribbons are observed by using 4294A impedance analyzer and magnetic force microscopy,respectively.The magneto-crystalline anisotropy field and stress anisotropy field of ribbons are analyzed by using X-ray diffraction,random anisotropy model,and numerical fitting.Meanwhile,the concept of magnetic anisotropy competing factor(k)is proposed,from the viewpoint of magnetic anisotropy,a mechanism for regulating giant magneto-impedance effect of ribbons prepared with multi-field coupling is studied.It is found that the longitudinally driven giant magneto-impedance effect gradually transforms from the single peak to dome-like with tensile stress increasing.However,a spike and dome-like giant magneto-impedance effect appears during such transformation,which is composed of two parts:spike-like top and dome-like base.Based on the magnetic domain structure of ribbons,it is found that the typical stress-annealed transversal magnetic domain structure is observed in ribbons of k≤0.147,while nucleation and splitting phenomenon of new domains are observed at the transversal magnetic domain wall in ribbons of k>0.147.Both longitudinally driven giant magneto-impedance effect and domain structures provide evidence to support the competing inhibition effect of magnetic anisotropy which exists in Fe-based alloy ribbon.Therefore,it is suggested that Fe-based alloys exhibit excellent stress-sensitive properties that can be understood by the competing inhibition effects of magnetic anisotropy.It is further shown that the competing inhibition effect of magnetic anisotropy is the main reason for regulating the giant magneto-impedance effect of soft magnetic materials.This multi-field coupling Fe-based alloy has good application prospects in regulating magnetic properties of magnetic materials.