Pham Yen Thi Hai, Liu Mingzu, Jimenez Valery Ortiz, Yu Zhuohang, Kalappattil Vijaysankar, Zhang Fu, Wang Ke, Williams Teague, Terrones Mauricio, Phan Manh-Huong
Department of Physics, University of South Florida, Tampa, FL, 33620, USA.
Department of Physics, The Pennsylvania State University, University Park, PA, 16802, USA.
Adv Mater. 2020 Nov;32(45):e2003607. doi: 10.1002/adma.202003607. Epub 2020 Oct 5.
The outstanding optoelectronic and valleytronic properties of transition metal dichalcogenides (TMDs) have triggered intense research efforts by the scientific community. An alternative to induce long-range ferromagnetism (FM) in TMDs is by introducing magnetic dopants to form a dilute magnetic semiconductor. Enhancing ferromagnetism in these semiconductors not only represents a key step toward modern TMD-based spintronics, but also enables exploration of new and exciting dimensionality-driven magnetic phenomena. To this end, tunable ferromagnetism at room temperature and a thermally induced spin flip (TISF) in monolayers of V-doped WSe are shown. As vanadium concentration increases, the saturation magnetization increases, which is optimal at ≈4 at% vanadium; the highest doping level ever achieved for V-doped WSe monolayers. The TISF occurs at ≈175 K and becomes more pronounced upon increasing the temperature toward room temperature. The TISF can be manipulated by changing the vanadium concentration. The TISF is attributed to the magnetic-field- and temperature-dependent flipping of the nearest W-site magnetic moments that are antiferromagnetically coupled to the V magnetic moments in the ground state. This is fully supported by a recent spin-polarized density functional theory study. The findings pave the way for the development of novel spintronic and valleytronic nanodevices and stimulate further research.
过渡金属二硫属化物（TMDs）优异的光电和谷电子特性引发了科学界的广泛研究。在TMDs中诱导长程铁磁性（FM）的一种方法是引入磁性掺杂剂以形成稀磁半导体。增强这些半导体中的铁磁性不仅是迈向基于TMD的现代自旋电子学的关键一步，还能够探索新的、令人兴奋的维度驱动磁现象。为此，展示了在V掺杂的WSe单层中室温下的可调铁磁性和热诱导自旋翻转（TISF）。随着钒浓度的增加，饱和磁化强度增加，在钒含量约为4 at%时达到最佳；这是V掺杂WSe单层迄今实现的最高掺杂水平。TISF发生在约175 K，并随着温度升高至室温而变得更加明显。TISF可以通过改变钒浓度来操控。TISF归因于与基态V磁矩反铁磁耦合的最近W位磁矩的磁场和温度依赖性翻转。这得到了最近一项自旋极化密度泛函理论研究的充分支持。这些发现为新型自旋电子和谷电子纳米器件的开发铺平了道路，并激发了进一步的研究。
