Yao Fen, Meng Junling, Zhang Lifang, Liu Xiaojuan, Meng Jian, Zhang Hongjie
State Key Laboratory of Rare Earth Resource Utilization Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, P. R. China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
Chemphyschem. 2019 May 3;20(9):1145-1152. doi: 10.1002/cphc.201900049. Epub 2019 Apr 8.
By first-principles calculations, lanthanide contraction is applied on a 1/1 (with symmetric center) and a 2/2 (with non-centrosymmetric polar structure) RTiO /RVO superlattices to realize quasi-continuous structural distortion modulation. The strong correlations of microscopic structural distortion, magnetic coupling and charge disproportionation accompanying metal-insulator transition (MIT) are clarified. It is found that the effect of lanthanide contraction on the 1/1 and 2/2 RTiO /RVO superlattices can induce ferromagnetic to antiferromagnetic transition within ab VO plane and the MIT occurs within these superlattices. And the MIT phenomenon is attributed to the charge disproportionation on V sites caused by the magnetic coupling transition. More structural distortion in the 2/2 RTiO /RVO superlattice is necessary than that of the 1/1 RTiO /RVO superlattice to induce the similar magnetic and MIT transition originating from the smaller interface/volume ratio. Based on these results, combining lanthanide contraction and epitaxial strain effects, multiferroic property is realized on 2/2 YTiO /YVO superlattice. Among all the structural parameters, aspect ratio c/a and Ti-O-V bond angles along the [001] direction are found to play the vital roles in the relevant transition process. Therefore, our calculations provide a microscopic guidance to design and synthesize new multiferroic materials.
通过第一性原理计算，将镧系收缩应用于1/1（具有对称中心）和2/2（具有非中心对称极性结构）的RTiO/RVO超晶格，以实现准连续的结构畸变调制。阐明了伴随金属-绝缘体转变（MIT）的微观结构畸变、磁耦合和电荷 disproportionation之间的强相关性。发现镧系收缩对1/1和2/2 RTiO/RVO超晶格的影响可在ab VO平面内诱导铁磁到反铁磁转变，且MIT发生在这些超晶格内。并且MIT现象归因于磁耦合转变引起的V位点上的电荷 disproportionation。由于界面/体积比更小，2/2 RTiO/RVO超晶格比1/1 RTiO/RVO超晶格需要更多的结构畸变来诱导类似的磁和MIT转变。基于这些结果，结合镧系收缩和外延应变效应，在2/2 YTiO/YVO超晶格上实现了多铁性。在所有结构参数中，发现纵横比c/a和沿[001]方向的Ti-O-V键角在相关转变过程中起着至关重要的作用。因此，我们的计算为设计和合成新型多铁性材料提供了微观指导。
