Wu Hongbo, Ma Fengxian, Tian Zhixue, Liu Ying, Jiao Yalong, Du Aijun
College of Physics, Hebei Key Laboratory of Photophysics Research and Application, Hebei Normal University, Shijiazhuang 050024, China.
School of Chemistry and Physics, Queensland University of Technology, Gardens Point Campus, Brisbane, QLD 4000, Australia.
Nanoscale. 2023 Jul 20;15(28):12078-12086. doi: 10.1039/d3nr01704d.
Two-dimensional (2D) ferromagnetic semiconductors are highly promising candidates for spintronics, but are rarely reported with direct band gaps, high Curie temperatures (), and large magnetic anisotropy. Using first-principles calculations, we predict that two ferromagnetic monolayers, BiXO (X = Ru, Os), are such materials with a direct band gap of 2.64 and 1.69 eV, respectively. Monte Carlo simulations reveal that the monolayers show high beyond 400 K. Interestingly, both BiXO monolayers exhibit out-of-plane magnetic anisotropy, with magnetic anisotropy energy (MAE) of 1.07 meV per Ru for BiRuO and 5.79 meV per Os for BiOsO. The estimated MAE for the BiOsO sheet is one order of magnitude larger than that for the CrI monolayer (685 μeV per Cr). Based on the second-order perturbation theory, it is revealed that the large MAE of the monolayers BiRuO and BiOsO is mainly contributed by the matrix element differences between d and d and d and d orbitals. Importantly, the ferromagnetism remains robust in 2D BiXO under compressive strain, while undergoing a ferromagnetic to antiferromagnetic transition under tensile strain. The intriguing electronic and magnetic properties make BiXO monolayers promising candidates for nanoscale electronics and spintronics.
二维（2D）铁磁半导体是自旋电子学极具潜力的候选材料，但具有直接带隙、高居里温度（）和大磁各向异性的报道却很少。通过第一性原理计算，我们预测两种铁磁单层材料BiXO（X = Ru，Os）就是这类材料，其直接带隙分别为2.64 eV和1.69 eV。蒙特卡罗模拟表明，这两种单层材料在400 K以上显示出高居里温度。有趣的是，BiXO两种单层材料均表现出平面外磁各向异性，对于BiRuO，每个Ru的磁各向异性能量（MAE）为1.07 meV，对于BiOsO，每个Os的磁各向异性能量为5.79 meV。BiOsO薄片的估计MAE比CrI单层（每个Cr为685 μeV）大一个数量级。基于二阶微扰理论，揭示出BiRuO和BiOsO单层材料的大MAE主要由d和d以及d和d轨道之间的矩阵元差异贡献。重要的是，2D BiXO在压缩应变下铁磁性保持稳健，而在拉伸应变下会发生铁磁到反铁磁的转变。这些有趣的电子和磁性特性使BiXO单层材料成为纳米级电子学和自旋电子学极具潜力的候选材料。
