多铁材料HoMnO3中光学吸收和畸变驱动的第一性原理研究

六角钙钛矿结构锰氧化物HoMnO₃磁电效应的研究近年来已成为多铁性材料研究中极其重要的一个方面. 本文基于广义梯度近似下的密度泛函理论, 考虑电子自旋的非共线磁性结构, 计算研究了 d电子在位库仑作用和自旋-轨道耦合作用对HoMnO₃的电子结构、 轨道杂化和能态密度分布的影响. 结果显示, 当考虑在位库仑排斥势U作用时, 强烈的Ho 5d与O(3, 4) 2p以及Mn 3d与O(1, 2) 2p间的轨道杂化是驱动HoMnO₃发生铁电畸变的根源, 此时能隙和能带的分布为解释实验中发现的强烈的光学吸收峰提供了理论依据, 而自旋-轨道耦合使得Mn 3d-O(3, 4) 2p在 ab平面内的轨道交迭略有增强, 平面内部分能带简并消除, HoMnO₃材料呈现典型的间接性能隙绝缘体特征. 关键词： 磁电效应 铁电畸变 态密度 光学吸收

Research on optical absorption and distortion driving in multiferroic HoMnO3 from the first principles

The study on magnetoelectric effect in hexagonal perovskite structure HoMnO₃ has become a very important aspect in the research of multiferroic materials. In this paper, using the first principles based on the generalized gradient approximation of density functional theory and considering the noncollinear magnetic structure calculation, the effects of the interation between on-site Coulomb of d electron and spin-orbit coupling on the electronic density of states and energy band structure of HoMnO₃ are calculated and investigated. The calculations show that due to the on-site Coulomb interaction, the strong hybridization of Ho 5d with O(3, 4) 2p and Mn 3d with O(1, 2) 2p orbits are considered as the origin of driving force for the ferroelectric distortion. At the same time, the distributions of the energy gap and energy band provide a theoretical support for the explanation of strong optical absorption peak in experiment. In addition, the spin-orbit coupling makes the orbital hybridization of Mn 3d with O(3, 4) 2p within the ab plane strengthened, and the partial energy degeneracy in the ab plane is eliminated. The HoMnO₃ is shown to possess the insulator characteristics of typical indirect energy gap.
Keywords： magnetoelectric effect ferroelectric distortion electron density of states optical absorption