Han Xiaocui, Cui Hong, Liu Bo, Tian Cunling, Wang Junzhong, Chen Hong, Yuan Hongkuan
School of Physical Science and Technology, Southwest University, Chongqing, 400715, People's Republic of China.
School of Mechanical Engineering, Shannxi University of Technology, Shannxi, 723001, People's Republic of China.
Sci Rep. 2018 Jun 21;8(1):9429. doi: 10.1038/s41598-018-27424-y.
Magnetic tunnel junctions (MTJs) with ferromagnetic electrodes possessing the strong perpendicular magnetocrystalline anisotropy (PMA) are of great interest as they have a potential for realizing next-generation high-density non-volatile memory and logic chips. To date, it is an urgent and critical issue to continuously promote the PMAs through feasible modifications such as the substitution of ferromagnetic layers as well as the overlayer coating on them. Here, we perform the relativistic first principles calculations of TM|L1-FePt|MgO sandwich systems, and demonstrate that the changes in PMAs by capping TM layers are always giant and positive, e.g., PMA of Fe|FePt|MgO, the largest one among all our studied systems, is about 2 times larger than that of FePt|MgO. The interfacial PMAs at TM|FePt and FePt|MgO interfaces are extracted to be 3.31~9.40 meV and 3.32 meV, respectively, which are at least 3 times larger than 0.93 meV/ML of interior FePt layer. We illustratively verify that PMAs of TM|FePt|MgO can be turned in a large range by varying the TM layer and in-plane strain. Our results and model analyses provide useful insights for how these magnetic quantities are linked, and pave a way for the promotion of PMAs of FePt-based heterostructures via contact with TM overlayers.
具有强垂直磁晶各向异性（PMA）的铁磁电极磁性隧道结（MTJ）因其具有实现下一代高密度非易失性存储器和逻辑芯片的潜力而备受关注。迄今为止，通过诸如铁磁层替代及其上覆盖层包覆等可行的改性方法持续提升PMA是一个紧迫且关键的问题。在此，我们对TM|L1-FePt|MgO三明治体系进行了相对论第一性原理计算，并证明通过覆盖TM层导致的PMA变化总是巨大且为正的，例如，Fe|FePt|MgO的PMA是我们所有研究体系中最大的，比FePt|MgO的PMA大约大2倍。提取得到TM|FePt和FePt|MgO界面处的界面PMA分别为3.31~9.40 meV和3.32 meV，这至少是内部FePt层的0.93 meV/ML的3倍。我们举例验证了通过改变TM层和面内应变，TM|FePt|MgO的PMA可以在很大范围内变化。我们的结果和模型分析为这些磁学量之间的关联提供了有用的见解，并为通过与TM覆盖层接触来提升基于FePt的异质结构的PMA铺平了道路。
