Insulator-Metal Transition Driven by Pressure and B-Site Disorder in Double Perovskite La2CoMnO6
Insulator-Metal Transition Driven by Pressure and B-Site Disorder in Double Perovskite La2CoMnO6
复制标题
双钙钛矿 La2CoMnO6 中压力和 B 位无序驱动的绝缘体-金属转变
DOI：
10.1002/jcc.22976
复制
发表时间：
2012-06-15
影响因子：
3
通讯作者：
Meng, Jian
中科院分区：
文献类型：
--
作者：
Lv, Shuhui;Liu, Xiaojuan;Meng, Jian
采用第一性原理计算方法系统研究了双钙钛矿氧化物La 2CoMnO 6（LCMO）的基态结构以及外压和反位无序对其的影响.在考虑电子关联和自旋-轨道耦合效应的情况下，我们发现LCMO呈现绝缘性，但在外加压力作用下，LCMO转变为半金属性。这种调谐伴随着Co2+从高自旋态（t（2g）（5）e（g）（2））到低自旋态（t（2g）（6）e（g）（1））的自旋态跃迁，这是因为在压力下晶场分裂的增强。利用平均场近似理论，预测了Co2+处于低自旋态时LCMO的居里温度高于处于高自旋态时的居里温度，这归因于Co-O和Mn-O键收缩引起的铁磁双交换作用增强以及Co-O-Mn键角在压力下的增大.我们还发现LCMO中的反位无序也能实现这种从绝缘态到半金属态的转变，这与反位Co从高态到低态的自旋态转变有关。研究表明，La ~（3+）取代离子半径较小的稀土离子，可以诱导Co的自旋态转变，从而使RE_2CoMnO_6成为一种有前途的半金属材料。(C)2012 Wiley Periodicals，Inc.
The ground state of double perovskite oxide La2CoMnO6 (LCMO) and how it is influenced by external pressure and antisite disorder are investigated systematically by first-principles calculations. We find, on the consideration of both the electron correlation and spin-orbital coupling effect, that the LCMO takes on insulating nature, yet is transformed to half metallicity once the external pressure is introduced. Such tuning is accompanied by a spin-state transition of Co2+ from the high-spin state (t(2g)(5)e(g)(2)) to low-spin state (t(2g)(6)e(g)(1)) because of the enhancement of crystal-field splitting under pressure. Using mean-field approximation theory, Curie temperature of LCMO with Co2+ being in low-spin state is predicted to be higher than that in high-spin state, which is attributed to the enhanced ferromagnetic double exchange interaction arising from the shrinkage of Co-O and Mn-O bonds as well as to the increase in bond angle of Co-O-Mn under pressure. We also find that antisite disorder in LCMO enables such transition from insulating to half-metallic state as well, which is associated with the spin-state transition of antisite Co from high to low state. It is proposed that the substitution of La3+ for the rare-earth (RE) ions with smaller ionic radii could open up an avenue to induce a spin-state transition of Co, rendering thereby the RE2CoMnO6 a promising half-metallic material. (C) 2012 Wiley Periodicals, Inc.