磁场退火对Co基熔体抽拉丝巨磁阻抗效应的影响

Influence of field annealing on giant magneto-impedance effect of Co-based melt extraction amorphous wires

对Co基熔体抽拉非晶丝进行了普通炉内退火和不同磁场强度(500Oe,1600Oe,4000Oe)下的横向和纵向磁场退火,利用HP4192阻抗分析仪和Lakeshore7407VSM分析了退火态样品的巨磁阻抗(GMI)效应和软磁性能.研究结果表明,纵向磁场降低了环向各向异性,纵向磁场退火样品GMI效应降低且GMI曲线为单峰,最大阻抗变化率ΔZ/Z为131%,磁场响应灵敏度为7%/Oe;而横向磁场提高了环向畴体积,增加了环向各向异性场,导致退火样品GMI曲线随频率升高由单峰转变为双峰,且GMI效应增强,10MHz时,最大阻抗变化率ΔZ/Z达到190%,对应磁场响应灵敏度达到26%/Oe.并应用趋肤效应模型初步分析了退火处理影响非晶丝GMI效应的机理.

In order to investigate the influence of anneal treatment on the Co-based melt extraction wires, the soft magnetic properties and giant magnet-impedance （GMI） effect of the annealed Co75Fe4.0Si8B12Nb1 wire are investigated. Samples are prepared using melt extraction technology in vacuum and annealed at 450℃ without magnetic field or with miagntic field either longitudinal or transverse to the axis of wire of strength from 500 Oe to 4000 Oe ,respectively. The magnetic softness and GMI response are measured using HP4192 Impedance Analyzer and Lakeshore7407 VSM. Test results show that the circular anisotropy and GMI response are reduced after longitudinal field anneal treatment . GMI profiles are single-peaked and the maximum impedance ratio ΔZ/Z is 1 31% and field sensitivity is 7%/Oe. The circular permeability and GMI response are improved after transverse field anneal treatments because of the increased circular anisotropy. At higher frequencies,the GMI profiles change from single-peaked to two-peaked after being annealed in strong transverse field. The circular permeability is increased and GMI effect gets stronger with the increase of current frequency and anneal field. The largest impedance ratio of 190% with a field sensitivity of 26%/Oe is obtained for the Co-based transverse field annealed wires at 10 MHz. The correlations between the circular permeability,the GMI effect and the current frequency are discussed in the light of a skin effect model.