分子束外延制备的垂直易磁化MnAl薄膜结构和磁性

Structural characterization and magnetic properties of perpendicularly magnetized MnAl films grown by molecular-beam epitaxy

系统地研究了利用分子束外延方法在GaAs(001)衬底上外延生长的MnAlx薄膜的结构和垂直易磁化特性随组分及生长温度的依赖关系.磁性测试表明,可在较大组分范围内(0.4 x 1.2)获得大矫顽力的垂直易磁化MnAlx薄膜,然而同步辐射X射线衍射和磁性测试发现当x 0.6时MnAl薄膜出现较多的软磁相,当x>0.9时,MnAl薄膜晶体质量和化学有序度逐渐降低,组分为MnAl0.9时制备的薄膜有最好的[001]取向.随着生长温度的增加,MnAl0.9薄膜的有序度、垂直磁各向异性常数、矫顽力和剩磁比均增加,350 C时制备的MnAl0.9薄膜化学有序度高达0.9,其磁化强度、剩磁比、矫顽力和垂直磁各向异性常数分别为265 emu/cm3、93.3%、8.3 kOe(1 Oe=79.5775 A/m)和7.74 Merg/cm3(1 erg=10 7J).不含贵金属及稀土元素、良好的垂直易磁化性质、与半导体材料结构良好的兼容性以及磁性能随不同生长条件的可调控性使得MnAl薄膜有潜力应用于多种自旋电子学器件.

Perpendicularly magnetized MnAlx thin films with different A1 contents have been epitaxied on tlaAs （001） substrates by a molecular-beam epitaxy system. Crystalline quality of MnAlx films is closely related to A1 content, and magnetic properties of MnAlx films are improved as crystalline quality of MnAtx rims increases. MnA10.9 film shows the best crystalline quality and magnetic property among all samples. So we grew MnA10.9 films at different growth temperatures to further optimize growth conditions. With increasing temperature, the chemical order parameter increases and the full width at half maximum of the （002） peak decreases, which reveal the improvement of crystalline quality. Higher perpendicular magnetization, coercivity and magnetic anisotropy are found as growth temperature increases. The best crystalline quality and perpendicularly magnetized properties are found at 350 ~C; the coercivity of 8.3 kOe, saturation magnetization of 265 emu/cm3, Mr/Ms of 0.933 and perpendicular magnetic anisotropy constant of 7.74 Merg/cm3 are achieved. These tunable perpendicularly magnetized properties and good compatibility associated with semiconductor materials make the noble-metal-free and rare-earth-free MnA1 films attractive in the application of spintronic devices.