过渡金属原子掺杂对二维CrBr_(3)电磁学性能的调控

Tunable electronic and magnetic properties of transition-metal atoms doped CrBr_(3) monolayer

近年来,二维铁磁材料由于其在自旋电子学领域中十分广阔的应用前景受到广泛关注.单层CrBr_(3)是具有本征铁磁性的半导体,是自旋电子器件的潜在候选材料.然而,单层CrBr_(3)的居里温度较低,限制了其在自旋电子器件领域的应用.本文基于密度泛函理论,研究了3d过渡金属(TM)原子(Sc,Ti,V,Cr,Mn,Fe,Co,Ni,Cu和Zn)掺杂单层CrBr_(3)的磁学和电学性能.计算结果表明,TM原子掺杂后,体系总磁矩呈现先增加再减小的趋势.并且TM原子掺杂能够显著提高单层CrBr_(3)的居里温度(TC),实现了铁磁稳定性的增强.其中,Sc掺杂CrBr_(3)体系的TC与本征CrBr_(3)相比提高了159%.铁磁稳定性的增强归因于掺杂体系(TM-CrBr_(3))中直接交换和超交换相互作用之间的竞争.此外,依赖于不同的TM原子掺杂,TM-CrBr_(3)体系表现出半金属性和自旋零带隙半导体性质.本文的研究结果为单层CrBr_(3)在纳米电子和自旋电子器件中的应用开辟了新的前景.

The CrBr_(3) monolayer is a two-dimensional semiconductor material with intrinsic ferromagnetism.However,the low Curie temperature of CrBr_(3) monolayer limits its practical development in innovative spintronic devices.The electronic and magnetic properties of transition-metal atoms doped CrBr_(3) monolayer have been systematically investigated by using the density functional theory calculations.The formation energy elucidates that all 3d transition metal(TM)atoms prefer to be doped in the middle of a hexagon(H)site of CrBr_(3) monolayer.And all the TM atoms,except the Zn atom,can bond strongly to the surrounding Cr atoms with sizable formation energy.The results also indicate that the magnetic moment of TM-CrBr_(3) system changes as a result of the charge transfer between TM atom and adjacent Cr atom.In addition,comparing with the intrinsic CrBr_(3),the T_(C) of TM-CrBr_(3) system increases significantly,which means that the ferromagnetic stability of CrBr_(3) monolayer is enhanced.In particular,the T_(C) of CrBr_(3) with Sc atom can be increased by 159%.The enhancement of ferromagnetism is mainly due to the competition between the direct exchange and the superexchange interaction.We also find that the electronic properties of the TM-CrBr_(3) systems are diverse.For example,Sc-,Ti-,V-,Mn-,Fe-,Co-,Ni-,Cu-and Zn-CrBr_(3) exhibit spin gapless semiconductor(SGS)properties with 100%spin polarization at Fermi level.The TM-CrBr_(3) system can be adjusted from semiconductor to half-metal when Cr atoms are doped into the CrBr_(3) monolayer.This work,together with recent achievements in the field of two-dimensional ferromagnetic materials,provides an experimentally achievable guide for realizing the preparation of TM-CrBr_(3) system with high Curie temperature.Moreover,the possibility of application of these systems in nanoelectronics and spintronics is increased.