Structure and transport properties of amorphous high-κ Al₂O₃

¹ Center for Quantum Transport and Thermal Energy Science, School of Physics and Technology, Nanjing Normal University - Nanjing 210023, China
² Hongzhiwei Technology (Shanghai) Co., Ltd. - Shanghai 201206, China
³ Department of Physics and International Centre for Quantum and Molecular Structures, Shanghai University 99 Shangda Road, Shanghai 200444, China
⁴ Department of Physics and the Center of Theoretical and Computational Physics, The University of Hong Kong Pokfulam Road, Hong Kong SAR, China

^(a) yinwang@shu.edu.cn

Received: 24 August 2018
Accepted: 15 November 2018

Abstract

We report the amorphous structure of Al₂O₃ and the transport properties of the Fe/amorphous Al₂O₃/Fe magnetic tunnel junction (MTJ) from first principles. The amorphous Al₂O₃ structure was generated by a heat and quench method via classical molecular dynamics, and the dielectric and transport properties were calculated from first principles. The tunnel magnetoresistance of the Fe/amorphous Al₂O₃/Fe MTJ is 25% under zero bias and then slightly increases to 28% at the bias of 0.1 V. It then decreases with the increasing bias and becomes negative when the applied bias exceeds 0.4 V due to the rapid increase of the spin-down current in the antiparallel configuration which is originated from the new transmission channel of minority electrons in the left lead introduced by the increasing bias. The spin-injection efficiency (SIE) is also calculated to study the spin-polarized current of the Fe/amorphous Al₂O₃/Fe system. It is found that the SIE coefficient is around 60% and 15% at equilibrium for the parallel and antiparallel configuration, respectively.