分子束外延制备的垂直易磁化MnAl薄膜结构和磁性

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MnAl_x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MnAl_x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MnAl_0.9时制备的薄膜有最好的001]取向. 随着生长温度的增加, MnAl_0.9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℃时制备的MnAl_0.9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265emu/cm³、93.3%、8.3kOe (1 Oe=79.5775A/m)和7.74Merg/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. 关键词： 分子束外延 大矫顽力材料 磁各向异性

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

Perpendicularly magnetized MnAl_x thin films with different Al contents have been epitaxied on GaAs (001) substrates by a molecular-beam epitaxy system. Crystalline quality of MnAl_x films is closely related to Al content, and magnetic properties of MnAl_x films are improved as crystalline quality of MnAl_x fims increases. MnAl_0.9 film shows the best crystalline quality and magnetic property among all samples. So we grew MnAl_0.9 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 τ(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℃; the coercivity of 8.3 kOe, saturation magnetization of 265 emu/cm³, M_r/M_s 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 MnAl films attractive in the application of spintronic devices.
Keywords： molecular-beam epitaxy high coercivity materials magnetic anisotropy