Gweon Hyung Keun, Lee Sang Yeop, Kwon Hee Young, Jeong Juyoung, Chang Hye Jung, Kim Kyoung-Whan, Qiu Zi Qiang, Ryu Hyejin, Jang Chaun, Choi Jun Woo
Center for Spintronics, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea.
Advanced Analysis Center, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea.
Nano Lett. 2021 Feb 24;21(4):1672-1678. doi: 10.1021/acs.nanolett.0c04434. Epub 2021 Feb 11.
van der Waals (vdW) magnetic materials provide an ideal platform to study low-dimensional magnetism. However, observations of magnetic characteristics of these layered materials truly distinguishing them from conventional magnetic thin film systems have been mostly lacking. In an effort to investigate magnetic properties unique to vdW magnetic materials, we examine the exchange bias effect, a magnetic phenomenon emerging at the ferromagnetic-antiferromagnetic interface. Exchange bias is observed in the naturally oxidized vdW ferromagnet FeGeTe, owing to an antiferromagnetic ordering in the surface oxide layer. Interestingly, the magnitude and thickness dependence of the effect is unlike those expected in typical thin-film systems. We propose a possible mechanism for this behavior, based on the weak interlayer magnetic coupling inherent to vdW magnets, demonstrating the distinct properties of these materials. Furthermore, the robust and sizable exchange bias for vdW magnets persisting up to relatively high temperatures presents a significant advance for realizing practical two-dimensional spintronics.
范德华（vdW）磁性材料为研究低维磁性提供了一个理想平台。然而，对于这些层状材料磁性特征的观察，却大多缺乏能将它们与传统磁性薄膜系统真正区分开来的内容。为了研究范德华磁性材料特有的磁性，我们研究了交换偏置效应，这是一种出现在铁磁 - 反铁磁界面的磁现象。在自然氧化的范德华铁磁体FeGeTe中观察到了交换偏置，这是由于表面氧化层中的反铁磁有序排列。有趣的是，该效应的大小和厚度依赖性与典型薄膜系统中预期的不同。基于范德华磁体固有的弱层间磁耦合，我们提出了这种行为的一种可能机制，证明了这些材料的独特性质。此外，范德华磁体强大且可观的交换偏置在相对较高温度下依然存在，这为实现实用的二维自旋电子学带来了重大进展。
