Co2FeGa/BaTiO3多铁隧道结中磁电耦合效应的第一性原理研究

First-Principles Study of Magnetoelectric Coupling Effect in Co2FeGa/BaTiO3 Multiferroic Tunnel Junctions

利用第一性原理研究了Co2FeGa/BaTiO3多铁隧道结(MFTJ)中的磁电耦合效应,以及中间势垒层BaTiO3(BTO)的铁电临界尺寸,构建了FeGa/TiO2与Co2/TiO2两种对称性界面结构的多铁隧道结模型.结果表明,FeGa/TiO2与Co2/TiO2界面模型的铁电临界尺寸分别是4个和2个BTO单胞.此外,发现磁电耦合效应主要是由界面原子上磁矩的差异导致的,它们对多铁隧道结中BTO的极化非常敏感,而且这种耦合还与界面相关原子的电子杂化程度有关.另外,不同界面模型磁电耦合强度也是不一样的,Co2/TiO2界面模型多铁隧道结的磁电耦合系数要远大于FeGa/TiO2界面模型多铁隧道结的磁电耦合系数.采用半金属Heusler合金电极的多铁隧道结有望为纳电子器件和自旋电子器件的应用提供新的方法.

In this paper,the magnetoelectric coupling effect in the Co2 FeGa/BaTiO3 multiferroelectric tunnel junction (MFTJ) and the ferroelectric critical thickness of the intermediate barrier layer BaTiO3 (BTO) were studied by using the first-principles.Here,we constructed the MFTJ model with two symmetrical interface structures,i.e.,FeGa/TiO2 and Co2 /TiO2 interface models.Our results show that the critical thickness of the ferroelectricity of the FeGa/TiO2 and the Co2 /TiO2 interface model are 4 and 2 BTO unit cells,respectively.Moreover,it can be found that the magnetoelectric coupling effect is mainly caused by the difference in magnetic moments on the interface atoms,which are very sensitive to the polarization of BTO in the MFTJ,and this coupling is also related to the degree of electron hybridization of the interface atoms.In addition,the magnetoelectric coupling strength of different interface models is also different.The magnetoelectric coupling coefficient of the MFTJ at the Co2 /TiO2 interface is much larger than that of the FeGa/TiO2 interface.MFTJ using semi-metal Heusler alloy electrodes are expected to provide new ways for the application of nanoelectronic devices and spintronic devices.