论文标题
铁电磁效果和磁性的首个主要研究，铁磁性半导体y $ _3 $ _3 $ fe $ _5 $ o $ $ $ _ {12} $和bi $ _3 $ _3 $ fe $ _5 $ _5 $ o $ $ $ _ {12} $
A First Principle Study on Magneto-Optical Effects and Magnetism in Ferromagnetic Semiconductors Y$_3$Fe$_5$O$_{12}$ and Bi$_3$Fe$_5$O$_{12}$
论文作者
论文摘要
磁光（MO）效应不仅是磁性固体的磁性和电子结构的强大探针，而且在高密度数据存储技术中具有宝贵的应用。 Yttrium Iron Garnet（Y $ _3 $ fe $ _5 $ o $ o $ _ {12} $）（Yig）和士兵铁石榴石（bi $ _3 $ _3 $ _3 $ fe $ _5 $ o $ $ $ _ {12} $）（big）是两个广泛使用的磁性半导体，具有强烈的磁性效果，并引起了对富有的良好的效果，并引起了人们的注意，并获得了罚款的研究。特别是，YIG通常被用作自旋电流喷油器。在本文中，我们基于密度函数理论，对YIG和BIG的磁性，电子，光学和MO性质进行了彻底的理论研究，并具有广义梯度近似以及现场库仑的排斥。我们发现，两个半导体都表现出很大的MO效应，其Kerr和Faraday旋转角与最著名的MO材料（如MNBI）相当。尤其是，在Photon Energy $ \ sim2.4 $ eV处的散装大型大范围-1.2 $ ^{\ circ} $的mo kerr旋转角度，而大胶片的Mo Faraday旋转角度达到-74.6 $ ^{\ circ}/μm$，photon Energy $ \ sim2.7 $ ev。此外，我们还发现，在大的MO带隙上的价和导带都是纯粹的旋转状态，即Big是一个单个旋转半导体。这些有趣的发现表明，铁石榴石将在半导体MO和Spintronic Nanodevices中找到有价值的应用。计算出的光导率光谱，Mo Kerr和Faraday旋转角与可用的实验数据一致。通过计算出的频带结构，尤其是通过确定带状态对称性和主要的光学转变，在布里群区域的$γ$点上分析了两个系统的光谱和MO光谱的主要特征。
The magneto-optical (MO) effects not only are a powerful probe of magnetism and electronic structure of magnetic solids but also have valuable applications in high-density data-storage technology. Yttrium iron garnet (Y$_3$Fe$_5$O$_{12}$) (YIG) and bismuth iron garnet (Bi$_3$Fe$_5$O$_{12}$) (BIG) are two widely used magnetic semiconductors with strong magneto-optical effects and have also attracted the attention for fundamental physics studies. In particular, YIG has been routinely used as a spin current injector. In this paper, we present a thorough theoretical investigation on magnetism, electronic, optical and MO properties of YIG and BIG, based on the density functional theory with the generalized gradient approximation plus onsite Coulomb repulsion. We find that both semiconductors exhibit large MO effects with their Kerr and Faraday rotation angles being comparable to that of best-known MO materials such as MnBi. Especially, the MO Kerr rotation angle for bulk BIG reaches -1.2$ ^{\circ}$ at photon energy $\sim2.4$ eV, and the MO Faraday rotation angle for BIG film reaches -74.6 $ ^{\circ}/μm$ at photon energy $\sim2.7$ eV. Furthermore, we also find that both valence and conduction bands across the MO band gap in BIG are purely spin-down states, i.e., BIG is a single spin semiconductor. These interesting findings suggest that the iron garnets will find valuable applications in semiconductor MO and spintronic nanodevices. The calculated optical conductivity spectra, MO Kerr and Faraday rotation angles agree well with the available experimental data. The main features in the optical and MO spectra of both systems are analyzed in terms of the calculated band structures especially by determining the band state symmetries and the main optical transitions at the $Γ$ point in the Brillouin zone.
