Prediction of bipolar <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>VSi</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>As</mml:mi><mml:mn>4</mml:mn></mml:msub></mml:mrow></mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>VGe</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>As</mml:mi><mml:mn>4</mml:mn></mml:msub></mml:mrow></mml:math> monolayers with high Curie temperature and strong magnetocrystalline anisotropy
Jinsen Zhang, Yao Wang, Chenqiang Hua, Shenbo Yang, Yujing Liu, Jianmin Luo, Tiefeng Liu, Jianwei Nai, Xinyong Tao
Abstract
Recent studies have demonstrated that two-dimensional intrinsic magnetic materials with high Curie temperature $({T}_{\text{c}})$ and large magnetic anisotropy energy (MAE) are highly desirable for future spintronics. After careful investigations through density functional theory, bipolar ${\mathrm{VSi}}_{2}{\mathrm{As}}_{4}$ and ${\mathrm{VGe}}_{2}{\mathrm{As}}_{4}$ monolayers, with semiconductor valence and conduction band edges fully spin polarized in different spin directions, are demonstrated to be highly stable and have in-plane ferromagnetism (FM) with large MAE of $\ensuremath{\sim}5.5$ meV. The FM interaction is found to be dominated by the superexchange between d orbitals of V atoms through p orbitals of anions. More interestingly, ${T}_{\text{c}}$ is estimated to be $\ensuremath{\sim}900$ K through Monte Carlo simulation, which is significantly higher than room temperature. In addition, both MAE and ${T}_{\text{c}}$ can be substantially regulated and increased under biaxial strain and the transition from FM semiconductors to metals will occur. Our calculations and analyses indicate that ${\mathrm{VSi}}_{2}{\mathrm{As}}_{4}$ and ${\mathrm{VGe}}_{2}{\mathrm{As}}_{4}$ monolayers are ideal systems for the fundamental understanding of magnetic physics as well as building blocks for magnetoelastic applications, high-temperature, or/and gate-tunable spintronic nanodevices.