BiFeO3基薄膜和异质结外电场下磁电响应及耦合研究

Based on density functional theory, we develop an improved slab model applying external electric field and aim to systematically investigate the magnetoelectric response and coupling effect involving electron transport, orbital reconstruction, spin tranfer,structural distortion, and ferroelectric response under external electric field in BiFeO3(BFO)-based films. Combined with the experimental methods,the slab model is used to reveal the mechanism of the magnetoelectric coupling effect mediated by spin,orbital,charge ordering,lattice, and electron transport under an external electric field in BFO-based films. This work is mainly focusing on the interaction and correlation among magnetic ordering, lattice distortion,ferroelectric charge ordering, and electron transport in magnetic ferroelectrics such as BFO-based films,and it will shed light on the understanding of the exchange-bias coupling involed in the BFO-based heterostructures and field-effect devices using the electric-field controllable magnetization. Hereby, it contributes a lot to the fabrication of high-density magnetic storage using electric-field tunable ferromagnetic magnetization reversal with lower energy consumption at room-temperature and has potential applications in the emerging field of spintronics.This work plays a crucial role in exploring the microscopic mechanism in magnetoelectric coupling and opens a new way towards manufacturing the novel multiferroics with excellent magnetoelectric coupling coefficient using the quantum manipulation within first-principles calculations.

本研究基于密度泛函理论，发展出描述BiFeO3(BFO)基薄膜多物理场耦合效应的外部电场平板模型,对BFO基薄膜和异质结外部电场下的电子输运、轨道重构、自旋输运、晶格畸变和铁电响应的相互作用和耦合机理进行系统而具有开创性的研究。旨在探索外部电场作用下磁序、晶格畸变、铁电和微观电子输运诱导的磁电耦合机理，理论结合实验揭示外电场下自旋、轨道、电荷序、晶格和电子输运之间相互耦合的微观物理机制。室温BFO基薄膜外电场下磁电耦合机理的揭示对理解BFO基异质结交换偏置机理，设计外电场调控铁磁序的室温"电写磁读"高密度低能耗磁存储器件和自旋电子器件提供材料基础。本研究对于进一步认识磁电耦合机理的物理内涵，采用第一性原理进行量子调控设计新的性能优良的室温强磁电耦合多铁性材料提供重要的理论指导。

基于密度泛函理论对BiFeO3 基薄膜和异质结外部电场下的电子输运、轨道重构、自旋输运、晶格畸变和铁电响应的相互作用和耦合机理进行系统的研究。证明了存在于BiFeO3强关联多铁性体系里面的磁电耦合现象，磁晶易轴的偏转源自于t2g轨道的重构；揭示了BiFeO3基异质结构薄膜的光生载流子输运机理；揭示钙钛矿基异质结构界面的载流子传输机理，系统全面的解释了钙钛矿体系的结构及对光学性质和载流子输运的影响。本研究为设计外电场调控铁磁序的室温“电写磁读”高密度低能耗磁存储器件和自旋电子器件提供材料基础。对于进一步认识磁电耦合机理的物理内涵，采用第一性原理进行量子调控设计新的性能优良的室温强磁电耦合多铁性材料提供重要的理论指导，同时对钙钛矿体系光伏性能提升和光伏器件的设计制备具有重要的指导意义。