真空退火对周期性界面掺杂Ni_(80)Co_(20)薄膜磁性的影响

EFFECT OF ANNEALING ON THE MAGNETIC PROPERTIES OF Ni_(80)Co_(20) THIN FILMS WITH IMPURITY LAYERS

用磁控溅射方法制备了两个具有不同Fe层厚度的 [Ni80 Co2 0 (L) /Fe(tFe) ]N 多层膜系列样品 ,其中tFe=0 1和 2nm .研究了两个系列样品的磁及输运性质随Ni80 Co2 0 层厚度L的变化关系 .在退火态 [Ni80 Co2 0 (L) /Fe(0 1nm) ]N 系列样品中 ,发现各向异性磁电阻 (AMR)和横向磁电阻 (TMR)在L为 10nm附近存在一较宽的增强峰 ,其峰位与制备态 [Ni80 Co2 0 (L) /Fe(2nm) ]2 5多层膜TMR的增强峰位一致 .当L小于Ni80 Co2 0 合金的电子平均自由程时 ,制备态 [Ni80 Co2 0 (L) /Fe(0 1nm) ]N 样品的各向异性磁电阻 (Δρ)和零场电阻率 ρ都随L的减小而增加 ,且ρ的增量超过Δρ的增量 .ρ随L的依赖关系可采用Fuchs Sondheimer理论描述 .在L小于 10nm时 ,制备态界面掺杂 [Ni80 Co2 0 (L) /Fe(0 1nm) ]N 系列样品的矫顽力Hc 随L近似直线上升 ,在L大于 10nm后趋于饱和 .退火后Hc显著下降 .实验结果表明 ,在多层膜结构中 ,界面散射可导致 ρ和Δρ的增强 ;磁性合金界面层还可导致畴结构的改变及TMR和AMR的增强 .

The magnetic and transport properties of two series of sputtered [Ni 80 Co 20 (L) /Fe( t Fe )] N multilayers (MLs) with different Fe layer thickness of t Fe =0 1 and 2nm, and varying L were studied and compared with each other. An enhanced anisotropic magnetoresistance (AMR) peak around L =10nm was observed for annealed films with t Fe =0 1nm. The position of the enhanced AMR peak is the same as that of transversal MR peak for the deposited MLs with t Fe =2nm. For the as\|deposited films with impurity Fe layers, when L becomes lower than the electron mean free path of Ni 80 Co 20 alloy, the zero\|field resistivity ρ increases with decreasing L and the increase of ρ will exceed that of AMR (Δ ρ ). The L dependence of ρ can be described by Fuchs\|Sondheimer theory. The coercivity H c of the as\|deposited films with t Fe =0 1nm increases rapidly with increasing L for L <15nm and is almost saturated for L >15nm. The dependence of H c on L may be related to the interface structure of MLs, which is indicated by a big drop of H c in the annealed films. Our experimental data show that the interface scattering in MLs may increase AMR; the magnetic alloy interfacial layers in MLs may change the domain structure and enhance transverse MR and AMR.