Anatomy of Magnetic Anisotropy and Voltage-Controlled Magnetic Anisotropy in Metal Oxide Heterostructure from First Principles
Anatomy of Magnetic Anisotropy and Voltage-Controlled Magnetic Anisotropy in Metal Oxide Heterostructure from First Principles
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DOI：
10.3390/cryst10121118
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发表时间：
2020-12
期刊：
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通讯作者：
Indra Pardede;D. Yoshikawa;T. Kanagawa;N. Ikhsan;Masao Obata;T. Oda
中科院分区：
文献类型：
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作者：
Indra Pardede;D. Yoshikawa;T. Kanagawa;N. Ikhsan;Masao Obata;T. Oda
电压控制磁各向异性（VCMA）是磁隧道结（MTJ）磁电控制的一种很有前途的方法。在这里，我们系统地计算了磁各向异性（MA）和VCMA能量的众所周知的MTJ结构组成的Fe/MgO界面与Cr缓冲层。在此计算中，我们研究了Fe和Cr之间的合金化和应变效应。我们使用的自旋密度泛函方法，其中包括两个贡献磁晶各向异性能（MCAE）源于自旋轨道耦合和形状磁各向异性能从自旋偶极-偶极相互作用。在本方法中，MCAE部分，除了一个共同的计划的总能量，使用大正则力定理计划进行评估。在后一种方案中，可以对MA和VCMA进行原子分辨和k分辨分析。首先，我们发现，随着合金化的引入，垂直MCAE增加了两倍。接下来，随着应变的引入，我们发现MCAE随着压缩应变的增加而增加，最大值为2.2 mJ/m2。对于VCMA系数，随着压缩应变的增加，符号变为负值，并且绝对值增大到170 fJ/Vm的数值。通过原子分辨和k分辨分析，我们阐明了这些增强的MCAE和VCMA主要来自于Fe与MgO（Fe 1）的界面，并位于二维布里渊区的某些线。用二阶微扰理论中d轨道态之间的自旋-轨道耦合解释了MCAE和VCMA的结果。
Voltage control of magnetic anisotropy (VCMA) is one of the promising approaches for magnetoelectric control of magnetic tunnel junction (MTJ). Here, we systematically calculated the magnetic anisotropy (MA) and the VCMA energies in the well-known MTJ structure consisting of Fe/MgO interface with Cr buffer layer. In this calculation, we investigated an alloying between Fe and Cr and a strain effect. We used a spin density functional approach which includes both contributions from magnetocrystalline anisotropy energy (MCAE) originating from spin–orbit coupling and shape magnetic anisotropy energy from spin dipole–dipole interaction. In the present approach, the MCAE part, in addition to a common scheme of total energy, was evaluated using a grand canonical force theorem scheme. In the latter scheme, atom-resolved and k-resolved analyses for MA and VCMA can be performed. At first, we found that, as the alloying is introduced, the perpendicular MCAE increases by a factor of two. Next, as the strain is introduced, we found that the MCAE increases with increasing compressive strain with the maximum value of 2.2 mJ/m2. For the VCMA coefficient, as the compressive strain increases, the sign becomes negative and the absolute value becomes enhanced to the number of 170 fJ/Vm. By using the atom-resolved and k-resolved analyses, we clarified that these enhancements of MCAE and VCMA mainly originates from the Fe interface with MgO (Fe1) and are located at certain lines in the two dimensional Brillouin zone. The findings on MCAE and VCMA are fully explained by the spin-orbit couplings between the certain d-orbital states in the second-order perturbation theory.