Co-Ta-O颗粒膜的磁电阻效应研究

The Magnetoresistance Investigation of Co-Ta-O Insulating Granular Films

利用射频共溅射方法制备了一系列 Co- Ta- O介质颗粒膜 ,用 X射线能量色散谱和 X射线光电子谱分析了薄膜的成分和元素价态 ,用 X射线衍射测量了薄膜的晶体结构 .结果表明 ,Co- Ta-O颗粒膜系是由 Co颗粒镶嵌在非晶的氧化钽绝缘介质中而形成 .通过改变制备条件 ,研究了溅射电压和 Co成分对颗粒膜隧道磁电阻效应的影响 .发现磁电阻比值先随 Co成分的增加而增加 ,在Co原子个数比为 2 6 %时达最大值 ,后随 Co成分的进一步增加而减小 ;在 Co成分一定的情况下 ,低的溅射电压有利于获得大的隧道磁电阻比值 .

A series of Co Ta O granular films consisting of metal Co grains separated by Ta 2O 5 insulating matrix were fabricated by RF co sputtering method. X ray energy dispersion spectrum and X ray photoemission spectrum were employed to determine the composition and the valence of the films, while X ray diffraction was used to characterize the crystal structure of the films. The influences of the sputtering voltage and the Co composition on the tunnel magnetoresistance were systematically investigated. It was found that the value of TMR increased as the Co composition of the films got higher, and reached a maximum value at 26% Co, then decreased. At a certain Co composition, the sample prepared at lower sputtering voltage exhibited a larger TMR value.