Termination layer compensated tunnelling magnetoresistance in ferrimagnetic Heusler compounds with high perpendicular magnetic anisotropy.
Termination layer compensated tunnelling magnetoresistance in ferrimagnetic Heusler compounds with high perpendicular magnetic anisotropy.
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DOI：
10.1038/ncomms10276
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发表时间：
2016-01-18
影响因子：
16.6
通讯作者：
Parkin SS
中科院分区：
文献类型：
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作者：
Jeong J;Ferrante Y;Faleev SV;Samant MG;Felser C;Parkin SS
虽然高隧穿自旋极化已经在软性铁磁性的Heusler材料中被观察到，并预测了硬的铁磁性Heusler材料，但到目前为止，还没有实验观察到后者的高隧穿磁电阻。在这里，我们报告了在非晶衬底上制备高度织构的多晶Mn3Ge薄膜，具有超过7 T的非常高的磁各向异性，使其具有技术相关性。然而，我们发现的小而负的隧穿磁阻归因于主要来自低矩Mn-Ge端层的隧穿，这些端层与高矩Mn-Mn层相反。电流的净自旋极化反映了两个不同的终端层及其相关的隧穿矩阵元素的不同比例，这是由于不可避免的原子尺度粗糙度造成的。我们表明，通过工程的自旋极化的两个终端层是相同的符号，即使这些层是相反的磁化，高隧穿磁电阻是可能的。具有畸变四边形结构的Heusler合金薄膜由于其体垂直磁各向异性具有潜在的自旋电子学应用。在这里，作者证明了Mn3Ge薄膜具有较大的垂直磁各向异性，并伴有负隧穿磁阻。
Although high-tunnelling spin polarization has been observed in soft, ferromagnetic, and predicted for hard, ferrimagnetic Heusler materials, there has been no experimental observation to date of high-tunnelling magnetoresistance in the latter. Here we report the preparation of highly textured, polycrystalline Mn3Ge films on amorphous substrates, with very high magnetic anisotropy fields exceeding 7 T, making them technologically relevant. However, the small and negative tunnelling magnetoresistance that we find is attributed to predominant tunnelling from the lower moment Mn–Ge termination layers that are oppositely magnetized to the higher moment Mn–Mn layers. The net spin polarization of the current reflects the different proportions of the two distinct termination layers and their associated tunnelling matrix elements that result from inevitable atomic scale roughness. We show that by engineering the spin polarization of the two termination layers to be of the same sign, even though these layers are oppositely magnetized, high-tunnelling magnetoresistance is possible. Heusler alloy thin films with a distorted tetragonal structure have potential spintronics applications given their bulk perpendicular magnetic anisotropy. Here, the authors demonstrate large perpendicular magnetic anisotropy in Mn3Ge thin films accompanied by negative tunnelling magnetoresistance.