Unveiling the role of Co-O-Mg bond in magnetic anisotropy of Pt/Co/MgO using atomically controlled deposition and in-situ electrical measurement

TL;DR

This study investigates how Co-O-Mg bonds influence magnetic anisotropy at Pt/Co/MgO interfaces, revealing that specific atomic bonds significantly affect magnetic properties, with experimental and theoretical insights clarifying the underlying mechanisms.

Contribution

It provides new understanding of the atomic-scale role of Co-O-Mg bonds in magnetic anisotropy, combining in-situ measurements and ab initio calculations.

Findings

Chemisorbed oxygen reduces magnetic moment and anisotropy of Co surface.

Mg deposition can recover magnetic anisotropy after oxygen exposure.

Co(Fe)-O-M bonds are more influential than Co(Fe)-O bonds in magnetic anisotropy.

Abstract

Despite the crucial role of interfacial perpendicular magnetic anisotropy in Co(Fe)/MgO based magnetic tunnel junction, the underlying mechanism is still being debated. Here, we report an anatomical study of oxygen and Mg effect on Pt/Co bilayers through repeated in-situ anomalous Hall effect measurements, controlled oxygen exposure and Mg deposition in an ultrahigh vacuum system. We found that chemisorbed oxygen not only quenches the effective magnetic moment of the Co surface layer, but also softens its magnetic anisotropy. However, a subsequent Mg dusting on the oxygen pre-exposed Pt/Co surface can recover the magnetic anisotropy. The ab initio calculations on the exchange splitting and orbital hybridization near the Fermi level give a clear physical explanation of the experimental observations. Our results suggest that Co(Fe)-O-M bond plays a more important role than the widely perceived Co(Fe)-O bond does in realizing interfacial perpendicular magnetic anisotropy in Co(Fe)/MgO heterostructures.