Hf掺杂LaMnO3的第一性原理研究

深圳大学物理与光电工程学院,广东深圳518061

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

First-principles study on Hf doped LaMnO3
LÜShuyu,LI Jianwei,JIN Hao,WEI Yadong,and WANG Jian

College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518061, Guangdong Province, P. R. China

condensed matter theory; first-principles calculation; density functional theory; rare earth manganese oxide; Hf doping; perovskite; optical absorption; spin valve; magnetoresistance

DOI: 10.3724/SP.J.1249.2022.05489

备注

LaMnO3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LaMnO3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La1-xHfxMnO3的晶格结构和电子能带结构,以及La1-xHfxMnO3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La1-xHfxMnO3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,La1-xHfxMnO3的能带带隙与非掺杂本征体LaMnO3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,La1-xHfxMnO3光吸收边出现红移,光学带隙减小.利用La3/4Ba1/4MnO3作为左右导线、La3/4Hf1/4MnO3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~(2.8×105)%,通过门电压调控中心层,磁电阻可达~(5.1×105)%.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.
LaMnO3 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 LaMnO3, 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 La1-xHfxMnO3, as well as the spin valve device consisted of La1-xHfxMnO3 scattering region sandwiched by two Ba doped LaMnO3 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 La1-xHfxMnO3. Hf elements exist in La1-xHfxMnO3 as stable Hf 4+ions, showing the properties of n-type doping. When the HF doping concentration x is small (i.e. x≤0. 031), the bandgap of La1-xHfxMnO3 is close to that of the undoped intrinsic phase LaMnO3, and an isolated impurity level due to Hf doping is formed in the bandgap. The optical absorption spectrum of La1-xHfxMnO3 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 La3/4Ba1/4MnO3 as the left and right electrodes and La3/4Hf1/4MnO3 as the center layers is calculated, and the magnetoresistance near the Fermi level reaches about ~ (2. 8 × 105)% . Through the gate voltage manipulation, the magnetoresistance can reach up to~(5. 1×105)%. Our work provides a theoretical guideline for design of novel spintronic devices.
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