Co基Husler合金磁性薄膜的垂直磁各向异性、各向异性磁电阻与弱局域化效应的研究

Co-based Full-Heusler alloy magnetic half-metallic films have broad application prospects in spintronics devices. Our previous studies showed that the perpendicular magnetic anisotropy of Co2FeAl films tended to disappear with the orientation changing of buffer layer and the increasing of film thickness. Anisotropy magnetoresistance indicated the good uniformity of Co2FeAl film, and on behalf of the anisotropy interface magnetoresistance, the difference between polar and transverse magnetoresistance changed. Meanwhile, negative magnetoresistance representing weak localization effect has been observed. The project intends to explore the Co-based Full-Heusler alloy magnetic half-metallic Co2(Fe, Mn, Ti)(Al, Si, Ge) films in a systematic in-depth study. The preparation factors, such as elements proportion, substrate, buffer layer, depositing temperature, depositing thickness of films, and so on, will be researched systematically. The interrelated mechanism between coercivity, saturation magnetization, remanence ratio between each regulation parameters will be characterized. The optimal preparation parameters of films with perpendicular magnetic anisotropy will be explored. The temperature effect of perpendicular magnetic anisotropy will be established. On the basis of anisotropy magnetoresistance, the mechanism of half-metallic properties, uniformity of films and anisotropy interface magnetoresistance will be explored. The inherent relationship between weak localization effect antisite disorder, half-metallic properties and will be clarified.

Co基 Full-Heusler合金半金属磁性薄膜在自旋电子学器件中具有广阔的应用前景。我们前期的研究工作表明Co2FeAl薄膜垂直磁各向异性随缓冲层取向的改变或薄膜厚度的增加而趋于消失；同时各向异性磁电阻表明薄膜的均匀性较好并发现代表各向异性界面磁电阻的极向、横向磁电阻之差发生改变，同时出现负磁阻的弱局域化效应。本项目拟对Co基Full-Heusler合金半金属磁性Co2(Fe, Mn, Ti)(Al, Si, Ge)薄膜进行系统深入的研究。系统调控薄膜的成分比例、基片、缓存层、沉积温度和沉积厚度等制备条件因素，研究矫顽力、饱和磁化强度、剩磁比与各调控参数之间的相互关联机制，探索薄膜垂直磁各向异性获得的最优制备工艺，给出垂直磁各向异性的相关温度效应规律；基于各向异性磁电阻探索研究薄膜的半金属性、薄膜均匀性与各向异性界面磁电阻的内在规律与机制，阐明弱局域化效应与反位无序、半金属特性之间的内

Co基 Full-Heusler合金半金属磁性薄膜在自旋电子学器件中具有广阔的应用前景。三明治结构的Pt/Co基Heusler合金薄膜/Pt薄膜通过磁控溅射制备在MgO单晶基片上。沉积温度、Heusler合金薄膜厚度以及Pt过渡层的晶向对Co基Heusler合金薄膜的磁各向异性的影响。不同的沉积温度和过渡Pt层的取向可以诱导三明治Co基Heusler合金薄膜的磁各向异性。过渡Pt层为(111)取向时，三明治Co基Heusler合金薄膜具有垂直各向异性，然而当过渡Pt层为(001)取向时三明治Co基Heusler合金薄膜呈现面内各向异性。同时各向异性磁电阻表明薄膜的均匀性较好并发现代表各向异性界面磁电阻的极向、横向磁电阻之差发生改变，同时出现负磁阻的弱局域化效应。此外，在Si/SiO2基片上制备了不同厚度的Co基Heusler合金薄膜，并研究了其弱局域化效应。结果表明薄膜厚度可以明显影响Co基Heusler合金薄膜弱局域化效应。当厚度为0.8nm时，弱局域化效应不能被观察到。随着厚度的增加，弱局域化效应越来越强。我们认为弱局域化效应来源于局域下Co、Fe和Al原子排列的无序度导致的。通过退火处理后，Co基Heusler合金薄膜弱局域化效应的明显降低。另我们也利用磁控溅射制备了Heusler合金Mn2PtSn和六角结构MnNiGa薄膜，并对这两种薄膜的晶体结构、磁性和自旋相关输运的性质进行了深入研究。