Tivakornsasithorn Kritsanu, Yoo Taehee, Lee Hakjoon, Lee Sangyeop, Choi Seonghoon, Bac Seul-Ki, Lee Kyung Jae, Lee Sanghoon, Liu Xinyu, Dobrowolska M, Furdyna Jacek K
Department of Physics, Korea University, Seoul, 136-701, Korea.
Department of Physics, Faculty of Science, Mahidol University, Bangkok, 10400, Thailand.
Sci Rep. 2018 Jul 12;8(1):10570. doi: 10.1038/s41598-018-28882-0.
We report a detailed study of magnetization reversal in Fe/GaMnAs bilayers carried out by magnetotransport measurements. Specifically, we have used planar Hall resistance (PHR), which is highly sensitive to the direction of magnetization, and is therefore ideally suited for tracking magnetization as it reorients between successive easy axes in the two magnetic layers during reversal. These reorientations take place separately in the two magnetic layers, resulting in a series of different magnetization alignments (parallel or orthogonal) during reversal, providing a series of stable PHR states. Our results indicate that the magnetic anisotropy of the structure is dominated by cubic symmetry of both layers, showing two in-plane easy axes, but with significantly different energy barriers between the easy orientations. Importantly, a careful analysis of the PHR results has also revealed the presence of strong ferromagnetic interlayer exchange coupling (IEC) between the two magnetic layers, indicating that although magnetization reorients separately in each layer, this process is not independent, since the behavior of one layer is influenced by its adjacent magnetic neighbor. The ability to design and realize multiple PHR states, as observed in this investigation, shows promise for engineering Fe/GaMnAs bilayer structures for multinary magnetic memory devices and related multinary logic elements.
我们报告了一项通过磁输运测量对Fe/GaMnAs双层膜中磁化反转进行的详细研究。具体而言，我们使用了平面霍尔电阻（PHR），它对磁化方向高度敏感，因此非常适合在反转过程中跟踪磁化在两个磁性层中相继易轴之间重新定向时的情况。这些重新定向在两个磁性层中分别发生，导致反转过程中出现一系列不同的磁化排列（平行或正交），从而提供一系列稳定的PHR状态。我们的结果表明，该结构的磁各向异性由两层的立方对称性主导，显示出两个面内易轴，但易取向之间的能垒显著不同。重要的是，对PHR结果的仔细分析还揭示了两个磁性层之间存在强铁磁层间交换耦合（IEC），这表明尽管磁化在每层中分别重新定向，但这个过程并非独立，因为一层的行为会受到其相邻磁性层的影响。如本研究中所观察到的，设计和实现多个PHR状态的能力为用于多值磁存储器件和相关多值逻辑元件的Fe/GaMnAs双层结构工程展示了前景。
