Giant perpendicular magnetic anisotropy in Ir/Co/Pt multilayers
Giant perpendicular magnetic anisotropy in Ir/Co/Pt multilayers
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DOI：
10.1103/physrevmaterials.3.104419
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发表时间：
2019-10-25
影响因子：
3.4
通讯作者：
Hayashi, Masamitsu
中科院分区：
文献类型：
--
作者：
Lau, Yong-Chang;Chi, Zhengdong;Hayashi, Masamitsu
我们研究了由铁磁金属Co和具有强自旋轨道耦合的重金属（Pt和Ir）组成的多层膜的磁性。生长具有对称（ABA 堆叠）和不对称（ABC 堆叠）结构的多层，以研究结构反演对称性破缺的影响。我们比较了对称 Pt/Co/Pt、Ir/Co/Ir 多层膜和非对称 Pt/Co/Ir、Ir/Co/Pt 多层膜的垂直磁各向异性 (PMA) 能量。首先，使用有效 PMA 能量的 Co 层厚度依赖性来研究 PMA 的界面贡献。 Ir/Co/Pt、Pt/Co/Ir不对称结构与Pt/Co/Pt、Ir/Co/Ir对称结构之间的界面PMA的比较表明，与整体界面PMA相比，破坏的结构反演对称引起的PMA较小。其次，我们发现当铁磁层通过层间交换耦合（IEC）反铁磁耦合时，多层中的磁各向异性场显着增加。宏观自旋模型计算可以定性地解释各向异性场与 IEC 之间的关系。在所研究的结构中，不对称Ir/Co/Pt多层结构的IEC最大：交换耦合场超过3T，因此各向异性场接近10T。第三，比较不对称Ir/Co/Pt和Pt/Co/Ir结构，我们发现前者的IEC和在某种程度上界面PMA比后者更强。 X 射线磁圆二色性 (XMCD) 研究表明，Ir/Co/Pt 多层膜中 Pt 的邻近感应磁化强度大于倒置结构 (Pt/Co/Ir)，这可能部分解释了磁性能的差异。这些结果显示了 PMA、IEC 和邻近感应磁化强度之间的复杂关系，可用于设计具有独特磁特性的人造结构。
We have studied the magnetic properties of multilayers composed of ferromagnetic metal Co and heavy metals with strong spin orbit coupling (Pt and Ir). Multilayers with symmetric (ABA stacking) and asymmetric (ABC stacking) structures are grown to study the effect of broken structural inversion symmetry. We compare the perpendicular magnetic anisotropy (PMA) energy of symmetric Pt/Co/Pt, Ir/Co/Ir multilayers and asymmetric Pt/Co/Ir, Ir/Co/Pt multilayers. First, the interface contribution to the PMA is studied using the Co layer thickness dependence of the effective PMA energy. Comparison of the interfacial PMA between the Ir/Co/Pt, Pt/Co/Ir asymmetric structures and Pt/Co/Pt, Ir/Co/Ir symmetric structures indicate that the broken structural inversion symmetry induced PMA is small compared to the overall interfacial PMA. Second, we find the magnetic anisotropy field is significantly increased in multilayers when the ferromagnetic layers are antiferromagnetically coupled via interlayer exchange coupling (IEC). Macrospin model calculations can qualitatively account for the relation between the anisotropy field and the IEC. Among the structures studied, the IEC is the largest for the asymmetric Ir/Co/Pt multilayers: the exchange coupling field exceeds 3 T and consequently, the anisotropy field approaches 10 T. Third, comparing the asymmetric Ir/Co/Pt and Pt/Co/Ir structures, we find the IEC and, to some extent, the interface PMA are stronger for the former than the latter. X-ray magnetic circular dichroism (XMCD) studies suggest that the proximity-induced magnetization in Pt is larger for the Ir/Co/Pt multilayers than the inverted structure (Pt/Co/Ir), which may partly account for the difference in the magnetic properties. These results show the intricate relation between PMA, IEC, and the proximity-induced magnetization that can be exploited to design artificial structures with unique magnetic characteristics.