Study on current-perpendicular-to-plane GMR materials by using amorphous magnetic alloy based multilayrs

巨磁电阻效应（GMR）被发现后，人们迫切需要开发一种低场巨磁电阻材料来满足实际应用的需要，为此，我们研究了由软磁非晶合金和非晶材料组成的巨磁电阻多层膜和颗粒合金，因为即使在非晶状态下，高电阻率也能产生电流-周向-平面（CPP）巨磁电阻效应。在本研究中，我们详细研究了颗粒巨磁电阻的基本性质。结果表明：（1）在非晶或纳米晶Co-Al-O颗粒合金薄膜中发现了一种新的巨磁电阻，它由金属颗粒和磁性颗粒以及绝缘颗粒间组成。该系统可以预期显示低场CPP-GMR多层结构与感生磁各向异性的控制。（2）研究了Cr-Fe和Cu-Co中颗粒巨磁电阻的成分、磁场和温度依赖性，以及与上述新型巨磁电阻的关系。(3)By通过控制NiFeCo/Cu多层膜的感生磁各向异性，改善了磁化过程，使不适于实际应用的MR曲线的磁滞回线几乎为零。

Since the Giant Magnetoresistance (GMR) has been discovered, it is intensively required to develop a low field GMR material for many practical applications.For this purpose, we have been investigating GMR multilayrs and granular alloys which consist of soft magnetic amorphous alloys and nonmagnetic materials, because Current-Perpendicular-to-Plance (CPP) GMR can arise even in amorphous state with high electrical resistivity. In the present study, we have examined the basic properties on granular GMR in detail. The results obtained are as follows :(1)A new type of GMR has been discovered in two phase amorphous or nanocrystalline Co-Al-O granular alloy thin films, consisting of the metallic and magnetic grains and the insulating intergrains. This system can be expected to show low filed CPP-GMR in multilayred structure with a control of induced magnetic anisotropy.(2)Compositional, magnetic field and temperature dependences of granular GMR in Cr-Fe and Cu-Co have been studied, including the relations to the new type of GMR mentioned above.(3)By controlling induced magnetic anisotropy of NiFeCo/Cu multilayrs, the magnetization process has been improved and the hysteresis of MR curves, unsuitable to applications, has been reduced to nearly zero.