Chen Andy Paul, Feng Yuan Ping
NUS Graduate School of Integrative Sciences and Engineering, National University of Singapore, Singapore 117456, Singapore.
Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, Ohio 44106, United States.
ACS Appl Mater Interfaces. 2020 Jun 3;12(22):25383-25389. doi: 10.1021/acsami.0c02074. Epub 2020 May 21.
Electric-field control of magnetocrystalline anisotropy energy (MAE) is important for the optimal performance of the tunnel junction components of the STT-MRAM. In such a device, a high MAE of the free magnetic layer improves storage robustness, whereas a low MAE is also useful to keep energy expenditure in the switching process at a minimum. Using the frozen potential method to calculate the MAE of the CoFe layer, the electric-field control of MAE in the BaTiO/CoFe/(Hf, Ta, W, Re, Os, Ir, Pt, or Au) heterostructure is studied. Electric field tuning of MAE is determined to be possible through switching the direction of BaTiO ferroelectric polarization, although both the tuning effect and the MAE depend strongly on the choice of the 5d transition metal element in the capping layer. The results predict a complicated behavior of both MAE and the underlayer polarization effect as we progress down the 5d series of elements as the choice of the capping layer element. Using the second-order perturbation theoretical framework, this behavior can nevertheless be explained by mechanisms including CoFe/capping layer interface hybridization and 5d band-filling trends in the capping layer.
电场对磁晶各向异性能（MAE）的控制对于自旋转移力矩磁随机存取存储器（STT-MRAM）的隧道结组件的最佳性能至关重要。在这样的器件中，自由磁层的高MAE可提高存储稳定性，而低MAE对于将切换过程中的能量消耗保持在最低水平也很有用。利用冻结势方法计算CoFe层的MAE，研究了BaTiO/CoFe/（Hf、Ta、W、Re、Os、Ir、Pt或Au）异质结构中MAE的电场控制。尽管调谐效果和MAE都强烈依赖于覆盖层中5d过渡金属元素的选择，但通过切换BaTiO铁电极化方向确定MAE的电场调谐是可行的。结果预测，随着覆盖层元素选择沿5d元素系列向下推进，MAE和底层极化效应都会出现复杂的行为。然而，使用二阶微扰理论框架，这种行为可以通过包括CoFe/覆盖层界面杂化和覆盖层中5d能带填充趋势在内的机制来解释。
