Hf掺杂LaMnO_(3)的第一性原理研究  

First-principles study on Hf doped LaMnO_(3)

作　　者：吕书宇 李建伟[1] 金浩 卫亚东[1] 王健[1] LÜ Shuyu;LI Jianwei;JIN Hao;WEI Yadong;WANG Jian(College of Physics and Optoelectronic Engineering,Shenzhen University,Shenzhen 518061,Guangdong Province,P.R.China)

机构地区：[1]深圳大学物理与光电工程学院,广东深圳518061

出　　处：《深圳大学学报（理工版）》2022年第5期489-496,共8页Journal of Shenzhen University(Science and Engineering)

基　　金：深圳市科技研发资金资助项目(JCYJ20190808152801642);国家自然科学基金资助项目(12034014)。

摘　　要：LaMnO_(3)是一种钙钛矿结构的绝缘体,因具有很多优异的性质受到广泛关注,然而以往研究主要集中在LaMnO_(3)的p型掺杂,而针对其n型掺杂的研究相对较少.基于密度泛函理论的第一性原理计算,研究不同Hf掺杂浓度下La_(1-x)Hf_(x)MnO_(3)的晶格结构和电子能带结构,以及La_(1-x)Hf_(x)MnO_(3)的光吸收性质和其与Ba掺杂作为导线构成的同质三明治两端子器件的自旋阀性质.结果表明,Hf掺杂的La_(1-x)Hf_(x)MnO_(3)最稳定基态结构为反铁磁结构或者亚铁磁结构,而非铁磁体;Hf在体系中以稳定的+4价离子存在,展现出n型掺杂的性质;当掺杂浓度x≤0.031时,La_(1-x)Hf_(x)MnO_(3)的能带带隙与非掺杂本征体LaMnO_(3)的带隙相近,并在带隙中形成了孤立的杂质能级.光吸收谱计算结果表明,随着Hf掺杂浓度上升,La_(1-x)Hf_(x)MnO_(3)光吸收边出现红移,光学带隙减小.利用La_(3/4)Ba_(1/4)MnO_(3)作为左右导线、La_(3/4)Hf_(1/4)MnO_(3)作为中心层可以构建自旋阀器件,其费密能级处的磁电阻达到了~(2.8×10^(5))%,通过门电压调控中心层,磁电阻可达~(5.1×10^(5))%.研究结果可为后续设计新型自旋电子学器件提供理论参考.LaMnO_(3)is an insulator with perovskite structure,which attracts the intense attention due to its promising properties.However,the previous studies mainly focused on the p-type doping of LaMnO_(3),while the n-type doping is under investigated.The effects of doping with various concentrations on the lattice structure,energy band and optical absorption of La_(1-x)Hf_(x)MnO_(3),as well as the spin valve device consisted of La_(1-x)Hf_(x)MnO_(3)scattering region sandwiched by two Ba doped LaMnO_(3)probes,are studied by the first-principles calculations based on the density functional theory.The results show that the antiferromagnetic or ferrimagnetic structure rather than the ferromagnetic structure is the ground state for La_(1-x)Hf_(x)MnO_(3).Hf elements exist in La_(1-x)Hf_(x)MnO_(3)as stable Hf4+ions,showing the properties of n-type doping.When the HF doping concentration x is small(i.e.x≤0.031),the bandgap of La_(1-x)Hf_(x)MnO_(3)is close to that of the undoped intrinsic phase LaMnO_(3),and an isolated impurity level due to Hf doping is formed in the bandgap.The optical absorption spectrum of La_(1-x)Hf_(x)MnO_(3)shows that its optical absorption edge appears a red shift and the optical bandgap decreases with the increase of x.Meanwhile,the spin valve device composed of La_(3/4)Ba_(1/4)MnO_(3)as the left and right electrodes and La_(3/4)Hf_(1/4)MnO_(3)as the center layers is calculated,and the magnetoresistance near the Fermi level reaches about~(2.8×10^(5))%.Through the gate voltage manipulation,the magnetoresistance can reach up to~(5.1×10^(5))%.Our work provides a theoretical guideline for design of novel spintronic devices.

关 键 词：凝聚态理论 第一性原理计算 密度泛函理论 稀土锰氧化物 Hf掺杂 钙钛矿 光吸收 自旋阀 磁电阻 

分 类 号：O469[理学—凝聚态物理]