Construction of FeN alloy films with ultra-strong magnetism and tunable magnetic anisotropy for spintronic application
Construction of FeN alloy films with ultra-strong magnetism and tunable magnetic anisotropy for spintronic application
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DOI：
10.1016/j.jallcom.2017.07.127
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发表时间：
2017-11
影响因子：
6.2
通讯作者：
C. Feng;J. Yin;J. Niu;Qinghua Zhang;L. Gu;Feng Yang;Xiaolei Tang;Longxiang Xu;Kui Gong-Kui-Gon
中科院分区：
文献类型：
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作者：
C. Feng;J. Yin;J. Niu;Qinghua Zhang;L. Gu;Feng Yang;Xiaolei Tang;Longxiang Xu;Kui Gong-Kui-Gon
FeN合金薄膜是一种很有前景的自旋电子材料，具有理论上的超强磁性（饱和磁化强度MS和磁各向异性Keff）和高自旋极化，其依赖于N有序间隙占据程度（S）。然而，由于N有序活化能较高，实际FeN薄膜的S值大多低于35%，这限制了可实现的磁性和传输性能。因此，构建具有良好控制磁性和高效电子传输的 FeN 合金薄膜仍然是一个长期存在的挑战。在这里，我们通过应变工程来解决这个问题。使用 Fe/Cr 底层，我们在 FeN 晶格中引入了相当大的外延应变。事实证明，该菌株可有效将S值提升至60%以上，MS值从2.18T显着提高至2.81T（增量30%），Keff值有效可调范围为1.3∼2.2×106J/m3。此外，Cr 和 Fe16N2 之间匹配的能带对称性 (Δ5) 有利于自旋电子应用的有效电子传输。通过第一性原理计算模拟间隙分布，发现晶格应变降低了N间隙迁移的活化能，这是磁可调性的热力学驱动力。
FeN alloy film is a promising spintronic material with the theoretically ultra-strong magnetism (saturation magnetizationMSand magnetic anisotropyKeff) and high spin polarization, which relies on the degree of N ordering interstice occupancy (S). However, due to the high activation energy for N ordering, theSvalue of an actual FeN film is mostly lower than 35% and this restricts the achievable magnetism and transportation property. Thus, the construction of a FeN alloy film with well-controlled magnetism and efficient electronic transportation remains a long-standing challenge. Here, we tackle the problem by strain engineering. Using an Fe/Cr underlayer, we introduced a considerable epitaxial strain in the FeN lattice. The strain is proven to effectively promote theSvalue to over 60%, resulting in remarkable enhancement ofMSvalue from 2.18T to 2.81T (30% increment) and effective tunability ofKeffvalue ranging 1.3∼2.2 × 106J/m3. Besides, the matched energy band symmetry (Δ5) between Cr and Fe16N2facilitates the efficient electronic transportation for spintronic applications. By simulating interstice distribution with the first-principles calculations, the lattice strain is found to decrease the activation energy for N interstitial migration, which serves as a thermodynamic driving force for the magnetism tunability.