Graf M E, Di Napoli S, Barral M A, Saleh Medina L M, Negri R M, Sepliarsky M, Llois A M
Instituto de Física Rosario (CONICET-UNR), Rosario, Argentina.
J Phys Condens Matter. 2018 Jul 18;30(28):285701. doi: 10.1088/1361-648X/aac74f. Epub 2018 May 23.
In this work we study, by means of ab initio calculations, the structural, electronic and magnetic properties of Y-doped BiFeO compounds. We determine that there is a morphotropic phase boundary at an yttrium concentration of [Formula: see text], where the structure changes from R3c to Pnma. This structural transition is driven by the chemical pressure induced by the dopant. By analyzing the evolution of the oxygen octahedral tilts we find an enhanced antiferrodistortive distortion when increasing the Y-doping, together with a reduction of the ferroelectric distorsion, that gives rise to a smaller value of the electric polarization. These cooperative effects should lead to a larger canting of the Fe magnetic moments and to a larger ferromagnetic response in the R3c phase, as it is observed in the experiments.
在这项工作中，我们通过从头算计算研究了Y掺杂BiFeO化合物的结构、电子和磁性性质。我们确定在钇浓度为[公式：见原文]时存在一个同型相界，此时结构从R3c转变为Pnma。这种结构转变是由掺杂剂引起的化学压力驱动的。通过分析氧八面体倾斜的演变，我们发现随着Y掺杂量的增加，反铁电畸变增强，同时铁电畸变减小，这导致极化值变小。正如实验中所观察到的，这些协同效应应该会导致Fe磁矩的更大倾斜以及R3c相中有更大的铁磁响应。
