自旋对CrI_(3)电磁性能影响的第一性原理研究

The effect of spin for electromagnetic properties of CrI_(3)by first-principles study

CrI_(3)作为一种直接带隙的层状铁磁性材料,具有独特的磁性质和电子性质,在新一代纳米磁器件和光电器件领域有极大的潜在应用价值,得到了科研工作者的极大重视.本文基于第一性原理,探究了自旋对CrI_(3)的原子结构、稳定性、电子结构及磁性质的影响.首先,我们考虑了3种不同方法的优化过程,分别是非自旋极化优化(opt_(nospin))、自旋极化优化(opt_(mag))和自旋轨道耦合优化(opt_(soc)).就结构稳定性而言,在不同方法的优化中,opt_(mag)最稳定,而opt_(mag)和opt_(soc)仅在Cr-I-Cr键角上有0.2°的细微差别.对电子结构来说,在自旋极化和自旋轨道耦合下,3种方法优化后均为半导体(opt_(nospin)为间接带隙,opt_(mag)和opt_(soc)为直接带隙),且导带底和价带顶分别由Cr-d轨道和I-p轨道贡献.对磁性质来说,不同方法优化后体系均为铁磁态,海森堡模型模拟的结果发现opt_(mag)和opt_(soc)的居里温度(48 K)与磁光克尔效应测量的结果(45 K)相近.我们的结果表明,基于第一性原理的结构优化和静态计算中采用自旋极化和自旋轨道耦合能够得到与实验一致的结果.

CrI_(3),a layered ferromagnetic(FM)material with a direct band gap,has unique electronic and magnetic properties,and has great potential application value in the field of new generation nano-magnetic de⁃vices and optoelectronic devices,and has been paid great attention by researchers.Based on the firstprinciples,we investigate the effect of spin on the atomic structure,stability,electronic structures and mag⁃netic properties of CrI_(3).First,we consider three structures under the different optimization processes,namely non-spin-polarization optimization(opt_(nospin)),spin-polarization optimization(opt_(mag)),spin orbit coupling opti⁃mization(opt_(soc)).In terms of structural stability,opt_(mag) is energetically stable under different spin optimiza⁃tion.There is little difference of 0.2°between the bond angle of Cr-I-Cr for opt_(mag) and opt_(soc).As for electronic structures,all the structures are semiconductor structures(opt_(nospin) is indirect bandgap,opt_(mag) and opt_(soc) are di⁃rect bandgap)under the spin optimizations and spin orbit coupling(SOC)calculation.As same as the results in previous experiment,the conduction band minimum and the valence band maximum of CrI_(3)are contributed by the d orbital of Cr and the p orbital of I under the spin optimizations and SOC calculation,respectively.For magnetic properties,all the structures are FM states under different optimization.The Curie temperature(TC)of opt_(mag) and opt_(soc) is similar as magneto-optical Kerr effect measurement(45 K)under the Heisenberg model simulation.Based on the first-principles,the results of structural optimization and static calculation un⁃der spin polarization and SOC are consistent with experiments.