Interfacial giant tunnel magnetoresistance and bulk-induced large perpendicular magnetic anisotropy in (111)-oriented junctions with fcc ferromagnetic alloys: A first-principles study
Interfacial giant tunnel magnetoresistance and bulk-induced large perpendicular magnetic anisotropy in (111)-oriented junctions with fcc ferromagnetic alloys: A first-principles study
复制标题
面心立方铁磁合金 (111) 取向结中的界面巨隧道磁阻和体感大垂直磁各向异性：第一性原理研究
DOI：
10.1103/physrevb.103.064427
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发表时间：
2021
影响因子：
3.7
通讯作者：
Miura Yoshio
中科院分区：
文献类型：
--
作者：
Masuda Keisuke;Itoh Hiroyoshi;Sonobe Yoshiaki;Sukegawa Hiroaki;Mitani Seiji;Miura Yoshio
研究了一系列有序面心立方铁磁合金和沿着[111]方向的MgO势垒磁性隧道结的隧道磁电阻效应和磁晶各向异性。考虑不同合金的（111）取向MTJ，我们在第一性原理计算的基础上计算了它们的TMR比和磁晶各向异性。分析表明，与钴基合金（CoNi，CoPt，和CoPd）的MTJ具有高TMR比超过2000%。这些MTJ积极有利于Co-O界面，其中Co和O态之间的界面反键在费米能级周围形成。我们发现，反键态的共振隧穿，称为界面共振隧穿，是获得高TMR比的起源。这种机制与我们最近在简单Co/MgO/Co（111）MTJ [K.增田，物理修订版B 101，144404（2020）2469-995010.1103/PhysRevB.101.144404]。相反，不同的系统具有不同的自旋通道，其中界面共振隧穿发生;例如，隧穿主要发生在CoNi基MTJ中的多数自旋通道中，而它发生在CoPt基MTJ中的少数自旋通道中。这意味着，即使机制是相似的，不同的自旋通道在不同的系统中占主导地位的高TMR比。这种差异是由于在特定的Co态中不同的交换分裂导致了通过与O态的反键的隧穿。对磁晶各向异性的计算表明，许多合金具有较大的垂直磁各向异性（PMA）.特别是，CoPt具有最大的各向异性能值。我们进一步进行微扰分析的PMA的自旋轨道相互作用，并揭示了大PMA在CoPt和CoNi主要来源于自旋守恒的费米能级附近的微扰过程。
We study the tunnel magnetoresistance (TMR) effect and magnetocrystalline anisotropy in a series of magnetic tunnel junctions (MTJs) with-ordered fcc ferromagnetic alloys and MgO barrier along the [111] direction. Considering the (111)-oriented MTJs with differentalloys, we calculate their TMR ratios and magnetocrystalline anisotropies on the basis of the first-principles calculations. The analysis shows that the MTJs with Co-based alloys (CoNi, CoPt, and CoPd) have high TMR ratios over 2000%. These MTJs have energetically favored Co-O interfaces where interfacial antibonding between Coand Ostates is formed around the Fermi level. We find that the resonant tunneling of the antibonding states, called the interface resonant tunneling, is the origin of the obtained high TMR ratios. Such a mechanism is similar to that found in our recent work on the simple Co/MgO/Co(111) MTJ [K. Masuda , Phys. Rev. B 101, 144404 (2020)2469-995010.1103/PhysRevB.101.144404]. In contrast, different systems have different spin channels where the interface resonant tunneling occurs; for example, the tunneling mainly occurs in the majority-spin channel in the CoNi-based MTJ while it occurs in the minority-spin channel in the CoPt-based MTJ. This means that even though the mechanism is similar, different spin channels contribute dominantly to the high TMR ratio in different systems. Such a difference is attributed to the different exchange splittings in the particular Costates contributing to the tunneling though the antibonding with Ostates. Our calculation of the magnetocrystalline anisotropy shows that manyalloys have large perpendicular magnetic anisotropy (PMA). In particular, CoPt has the largest value of anisotropy energy. We further conduct a perturbation analysis of the PMA with respect to the spin-orbit interaction and reveal that the large PMA in CoPt and CoNi mainly originates from spin-conserving perturbation processes around the Fermi level.