Hu Lei, Wu Xuming, Feng Yulin, Liu Yuqi, Xu Zhiyuan, Gao Guoying
School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074, China.
College of Physical Science and Technology, Lingnan Normal University, Zhanjiang 524048, China.
Nanoscale. 2022 Jun 1;14(21):7891-7897. doi: 10.1039/d2nr01757a.
2D van der Waals magnets have been widely studied in spintronics because of their unique electronic properties, no dangling bonds, and ultra-clean interfaces. However, most of them possess low Curie temperatures. Motivated by the recent discovery of a near-room-temperature ferromagnetic semiconductor in monolayer GdI, we proposed the Au/GdI/Au vertical van der Waals junction and investigated the bias-voltage- and temperature-gradient-dependent spin transport characteristics using density functional theory and the non-equilibrium Green's function method. It is found that, like bulk GdI, the four-layer GdI in the central scattering region of the junction exhibits intralayer ferromagnetism with weak interlayer antiferromagnetic coupling. An almost 100% spin polarization can be obtained whether at a bias voltage or at a temperature gradient for the junction, while high tunneling magnetoresistances are observed in a large bias voltage range or in a large temperature gradient range, which can reach 29000% and 3600%, respectively. The junction also exhibits a thermal spin diode effect. These versatile bias voltage- and temperature gradient-driven spin transport properties are understood from the calculated spin-dependent band structure of layered GdI and the spin-dependent transmission spectrum and density of states of the junction. The present work highlights layered GdI as a promising magnetic tunnel barrier for van der Waals spintronic devices and spin caloritronic devices.
二维范德华磁体因其独特的电子特性、无悬键和超清洁界面而在自旋电子学中得到了广泛研究。然而，它们中的大多数居里温度较低。受单层GdI中近室温铁磁半导体这一最新发现的启发，我们提出了Au/GdI/Au垂直范德华结，并使用密度泛函理论和非平衡格林函数方法研究了其依赖于偏置电压和温度梯度的自旋输运特性。研究发现，与块状GdI一样，结的中心散射区域中的四层GdI表现出层内铁磁性以及较弱的层间反铁磁耦合。无论是在偏置电压下还是在温度梯度下，该结都能获得近乎100%的自旋极化，同时在大偏置电压范围或大温度梯度范围内观察到高隧穿磁电阻，分别可达29000%和3600%。该结还表现出热自旋二极管效应。通过计算分层GdI的自旋相关能带结构以及结的自旋相关透射谱和态密度，理解了这些由偏置电压和温度梯度驱动的多功能自旋输运特性。本工作突出了分层GdI作为范德华自旋电子器件和自旋热电子器件中一种有前景的磁隧道势垒的地位。
