Giant interfacial perpendicular magnetic anisotropy in MgO/CoFe/capping layer structures

TL;DR

This study uses first-principles calculations to identify capping materials that significantly enhance perpendicular magnetic anisotropy in MgO/CoFe structures, crucial for high-stability spintronic memory devices.

Contribution

It demonstrates the potential to achieve giant PMA in MgO/CoFe structures by selecting appropriate capping layers, especially Bi, which enhances thermal stability for STT-MRAM.

Findings

MgO/CoFe/Bi exhibits giant PMA of 6.09 mJ/m2

Hf, Ta, Os, Ir, and Pb also enhance PMA

The origin of MAE is linked to atomic layer and orbital contributions

Abstract

Magnetic tunnel junction (MTJ) based on CoFeB/MgO/CoFeB structures is of great interest due to its application in the spin-transfer-torque magnetic random access memory (STT-MRAM). Large interfacial perpendicular magnetic anisotropy (PMA) is required to achieve high thermal stability. Here we use first-principles calculations to investigate the magnetic anisotropy energy (MAE) of MgO/CoFe/capping layer structures, where the capping materials include 5d metals Hf, Ta, Re, Os, Ir, Pt, Au and 6p metals Tl, Pb, Bi. We demonstrate that it is feasible to enhance PMA by using proper capping materials. Relatively large PMA is found in the structures with capping materials of Hf, Ta, Os, Ir and Pb. More importantly, the MgO/CoFe/Bi structure gives rise to giant PMA (6.09 mJ/m2), which is about three times larger than that of the MgO/CoFe/Ta structure. The origin of the MAE is elucidated by examining the contributions to MAE from each atomic layer and orbital. These findings provide a comprehensive understanding of the PMA and point towards the possibility to achieve advanced-node STT-MRAM with high thermal stability.