界面散射对Ni_(80)Co_(20)/M(M=Co,Cr,Ag)多层膜各向异性磁电阻的影响

INFLUENCE OF THE INTERFACE ON THE ANISOTROPIC MAGNETORESISTANCE OF Ni_(80)Co_(20)/M(M=Co, Cr, Ag) MULTILAYERS

用磁控溅射方法制备了Ｎｉ８０Ｃｏ２０／Ｍ（Ｍ＝Ｃｏ，Ｃｒ，Ａｇ）多层膜样品系列，Ｃｏ，Ｃｒ，Ａｇ杂质层的标称厚度为０．１ｎｍ，研究了界面散射对多层膜的磁及输运性质的影响．零场电阻率ρ的测量结果表明，对含Ｃｒ样品，ρ随杂质层间距Ｌ的依赖关系能较好的用Ｆｕｃｈｓ－Ｓｏｎｄｈｅｉｍｅｒ（Ｆ－Ｓ）理论描述．而对含Ｃｏ和Ａｇ样品，ρ随Ｌ的依赖关系在Ｌ小于１５ｎｍ时开始偏离Ｆ－Ｓ理论．磁电阻测量表明，含Ｃｒ和Ａｇ样品，各向异性磁电阻Δρ在Ｌ＜１５ｎｍ时随Ｌ的减小陡然下降．对含磁性Ｃｏ元素的样品，其Δρ值在Ｌ＞１５ｎｍ时高于Ｎｉ８０Ｃｏ２０单层薄膜的Δρ值；在Ｌ＜１５ｎｍ时Δρ值随Ｌ呈现振荡变化的趋势．磁性测量表明，三个系列样品的矫顽力Ｈｃ在Ｌ＜１５ｎｍ时都随Ｌ近似直线上升，在Ｌ＞１５ｎｍ后趋于饱和；经４００℃真空退火后Ｈｃ都显著下降．

Ni80Co20/M(M=Co, Cr, Ag) multilayers were prepared by magnetron sputtering with the nominal thickness of 0.1 nm for Co, Cr and Ag impurity layers and the influence of the interface on the magnetic and transport properties was studied. The measurements of the resistivity rho in zero field show that the dependence of rho on spacing of impurity layers, L, can be described by the Fuchs-Sondheimer (F-S) theory for Ni80Co20/Cr series. When L became smaller than 15 nm, the L dependence of rho for Ni80Co20/Co and Ni80Co20/Ag multilayers began to deviate from F-S description. The anisotropic magnetoresistance (AMR) measurements show that no AMR (Delta rho) enhancement was observed for samples with Cr and Ag, and both Delta rho and Delta rho/rho decrease rapidly with decreasing L for L < 15 nm. However, Delta rho of Ni80Co20(L)/Co multilayer is larger than that of Ni80Co20 film when L > 15 nm, and when L < 15 nm Delta rho oscillate with L with an approximate period of 4 nm. The coercivities H-c of three series of as-deposited films increase rapidly with increasing L for L < 15 mn and almost saturate for L > 15 nm. The dependence of H-c on L is related to the interface structure of multilayers, which can be indicated by a big drop of H-c when the films are annealed.