交流电流对铁基纳米晶丝巨磁阻抗效应形貌的影响

Influence of AC current on the profile of GMI effect in Fe-based nanocrystalline wire

本文研究了交流电流的大小(I=0.2—20mA)和频率(f=1—1MHz)对具有横向畴结构的铁基纳米晶丝的巨磁阻抗效应形貌的影响.实验结果表明,样品的巨磁阻抗效应呈双峰特征,随着频率的增大,双峰的位置H=±Hm向高场移动;但随着电流的增大,双峰的位置逐渐向中心(H=0)收缩,甚至变成单峰位形.理论上一般认为,双峰的位置与横向各向异性场Hk相对应,即Hm=Hk.然而,我们发现这一结果只在交流电流很小的情况下才成立.从转动磁化过程中能量极小的原理出发,给出了双峰的位置为Hm=Hkcos3θ,θ为饱和磁化强度与丝轴的夹角.根据这一关系,定性地解释了实验结果.

The influence of AC current （ with amplitud of Iac = 0. 2—20 mA and frequency of f = 1 kHz—1 MHz） upon the profile of gian magnetoimpedance （GMI） effect of a Fe-based nanocrystalline wire with transverse domain structure have been investigated. The experiment indicates that the GMI effect of the sample exhibits a two-peak feature. With the increasing of f,the peak field Hm increases,while Hm decreases even to H = 0 when Iac increases. According to the current theoretical models,the peak field Hm should conrrespond to the transverse anisotropy field Hk,Hm = Hk. However,we found that this conclusion is correct only for the case of very small AC current. So a relationship Hm = Hk cos3θ,where θ is the angle between saturation magnetisation and the axis of wire,has been deduced by minimizing the energy in the process of magnetisation rotation. The experiments can be explained by this result.