Yang C-H, Seidel J, Kim S Y, Rossen P B, Yu P, Gajek M, Chu Y H, Martin L W, Holcomb M B, He Q, Maksymovych P, Balke N, Kalinin S V, Baddorf A P, Basu S R, Scullin M L, Ramesh R
Department of Physics, University of California, Berkeley, California 94720, USA.
Nat Mater. 2009 Jun;8(6):485-93. doi: 10.1038/nmat2432. Epub 2009 Apr 26.
Many interesting materials phenomena such as the emergence of high-Tc superconductivity in the cuprates and colossal magnetoresistance in the manganites arise out of a doping-driven competition between energetically similar ground states. Doped multiferroics present a tantalizing evolution of this generic concept of phase competition. Here, we present the observation of an electronic conductor-insulator transition by control of band-filling in the model antiferromagnetic ferroelectric BiFeO3 through Ca doping. Application of electric field enables us to control and manipulate this electronic transition to the extent that a p-n junction can be created, erased and inverted in this material. A 'dome-like' feature in the doping dependence of the ferroelectric transition is observed around a Ca concentration of approximately 1/8, where a new pseudo-tetragonal phase appears and the electric modulation of conduction is optimized. Possible mechanisms for the observed effects are discussed on the basis of the interplay of ionic and electronic conduction. This observation opens the door to merging magnetoelectrics and magnetoelectronics at room temperature by combining electronic conduction with electric and magnetic degrees of freedom already present in the multiferroic BiFeO3.
许多有趣的材料现象，如铜酸盐中高温超导性的出现以及锰酸盐中的巨磁电阻，都源于能量相近的基态之间由掺杂驱动的竞争。掺杂多铁性材料展现了这种相竞争通用概念的诱人演变。在此，我们展示了通过在反铁磁铁电体BiFeO₃中进行Ca掺杂来控制能带填充从而实现电子导体 - 绝缘体转变的观测结果。施加电场使我们能够控制和操纵这种电子转变，以至于在这种材料中可以创建、消除和反转一个p - n结。在大约1/8的Ca浓度附近观察到铁电转变的掺杂依赖性呈现出“穹顶状”特征，此时出现了一个新的伪四方相，并且传导的电调制得到优化。基于离子传导和电子传导的相互作用讨论了所观察到的效应的可能机制。这一观测结果为通过将电子传导与多铁性BiFeO₃中已有的电和磁自由度相结合，在室温下融合磁电体和磁电子学打开了大门。
