热氧化硅衬底上制备的超薄cu2sb型(Mn-Cr)AlGe薄膜的垂直磁各向异性

T. Kubota, K. Ito, R. Umetsu, K. Takanashi
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引用次数: 4

摘要

垂直磁化薄膜具有小的饱和磁化强度$M_\ mathm {s}$,是自旋转移转矩写入型磁阻随机存取存储器(stt - mrm)的必要材料。本文研究了Cu$_2$ sb型晶体结构的金属间化合物{(Mn-Cr)AlGe},作为具有低$M_\mathrm{s}$ ($\sim 300$ kA/m)和高垂直磁各向异性$K_\mathrm{u}$的材料。在热氧化硅衬底上制备薄膜样品,研究了$K_\ mathm {u}$的层厚依赖关系和(Mn-Cr)AlGe$|$MgO界面顶部和底部的mg插入层的影响,以实现在几纳米厚度范围内的高$K_\ mathm {u}$。底部和顶部界面的最佳mg插入厚度分别为1.4 nm和3.0 nm,与以往类似的磁性隧道结插入效果研究结果相比,该厚度相对较厚。横截面透射电镜图像显示,镁插入层对al原子的相互扩散和MgO层的氧化起着屏障作用。在室温下,5 nm和3 nm厚度的(Mn-Cr)AlGe薄膜的$K_\ maththrm {u}$分别约为$7 × 10^5$和$2 × 10^5$ J/m$^3$,此时插入mg的厚度最佳。在几个纳米厚度上的$K_\ mathm {u}$与常规用于mram的垂直磁化CoFeB薄膜的值相当或更高,而$M_\ mathm {s}$值比CoFeB薄膜的值小三分之一或更小。所制备的(Mn-Cr)AlGe薄膜不仅具有磁性,而且在薄膜制备过程中与硅工艺的相容性也很好。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Perpendicular magnetic anisotropy in ultra-thin Cu2Sb-type (Mn–Cr)AlGe films fabricated onto thermally oxidized silicon substrates
Perpendicularly magnetized films showing small saturation magnetization, $M_\mathrm{s}$, are essential for spin-transfer-torque writing type magnetoresistive random access memories, STT-MRAMs. An intermetallic compound, {(Mn-Cr)AlGe} of the Cu$_2$Sb-type crystal structure was investigated, in this study, as a material showing the low $M_\mathrm{s}$ ($\sim 300$ kA/m) and high-perpendicular magnetic anisotropy, $K_\mathrm{u}$. The layer thickness dependence of $K_\mathrm{u}$ and effects of Mg-insertion layers at top and bottom (Mn-Cr)AlGe$|$MgO interfaces were studied in film samples fabricated onto thermally oxidized silicon substrates to realize high-$K_\mathrm{u}$ in the thickness range of a few nanometer. Optimum Mg-insertion thicknesses were 1.4 and 3.0 nm for the bottom and the top interfaces, respectively, which were relatively thick compared to results in similar insertion effect investigations on magnetic tunnel junctions reported in previous studies. The cross-sectional transmission electron microscope images revealed that the Mg-insertion layers acted as barriers to interdiffusion of Al-atoms as well as oxidization from the MgO layers. The values of $K_\mathrm{u}$ were about $7 \times 10^5$ and $2 \times 10^5$ J/m$^3$ at room temperature for 5 and 3 nm-thick (Mn-Cr)AlGe films, respectively, with the optimum Mg-insertion thicknesses. The $K_\mathrm{u}$ at a few nanometer thicknesses is comparable or higher than those reported in perpendicularly magnetized CoFeB films which are conventionally used in MRAMs, while the $M_\mathrm{s}$ value is one third or less smaller than those of the CoFeB films. The developed (Mn-Cr)AlGe films are promising from the viewpoint of not only the magnetic properties, but also the compatibility to the silicon process in the film fabrication.
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