MnGa-based fully perpendicular magnetic tunnel junctions with ultrathin Co2MnSi interlayers

Siwei Mao,Jianbai Xia,Jian Liu,Jianhua Zhao,Xiaolei Wang,Dahai Wei,Jun Lu,Xupeng Zhao

doi:10.1038/srep43064

Abstract

Because tetragonal structured MnGa alloy has intrinsic (not interface induced) giant perpendicular magnetic anisotropy (PMA), ultra-low damping constant and high spin polarization, it is predicted to be a kind of suitable magnetic electrode candidate in the perpendicular magnetic tunnel junction (p-MTJ) for high density spin transfer torque magnetic random access memory (STT-MRAM) applications. However, p-MTJs with both bottom and top MnGa electrodes have not been achieved yet, since high quality perpendicular magnetic MnGa films can hardly be obtained on the MgO barrier due to large lattice mismatch and surface energy difference between them. Here, a MnGa-based fully p-MTJ with the structure of MnGa/Co2MnSi/MgO/Co2MnSi/MnGa is investigated. As a result, the multilayer is with high crystalline quality, and both the top and bottom MnGa electrodes show well PMA. Meanwhile, a distinct tunneling magnetoresistance (TMR) ratio of 65% at 10 K is achieved. Ultrathin Co2MnSi films are used to optimize the interface quality between MnGa and MgO barrier. A strong antiferromagnetic coupling in MnGa/Co2MnSi bilayer is confirmed with the interfacial exchange coupling constant of −5erg/cm2. This work proposes a novel p-MTJ structure for the future STT-MRAM progress.

Highlights

CoFe and the TMR ratio was observed to be 23% at 10 K15
We present the realization of all bulk MnGa-based fully p-magnetic tunnel junctions (MTJs) with the core structure of Mn3.1Ga(23 nm)/Co2MnSi(0.6 nm)/MgO(1.8 nm)/Co2MnSi(0.6 nm)/Mn2.9Ga(12 nm)
The whole structure is grown on GaAs (001) substrates by molecular-beam epitaxy (MBE) system with two chambers (VG80) without being exposed to the air during the entire process

Summary

Introduction

CoFe and the TMR ratio was observed to be 23% at 10 K15. they tried to fabricate perpendicular magnetic tunnel junction (p-MTJ) structures such as MnGa/FM/MgO/CoFeB with TMR ratio up to 50% at room temperature[16,17]. They tried to fabricate perpendicular magnetic tunnel junction (p-MTJ) structures such as MnGa/FM/MgO/CoFeB with TMR ratio up to 50% at room temperature[16,17]. We choose ultrathin half-metallic Heusler compound Co2MnSi films as interlayers to reduce the lattice mismatch between MgO barrier and MnGa electrodes as well as to enhance the TMR ratio.

Results

Conclusion