Sign change in the tunnel magnetoresistance of Fe3O4/MgO/Co-Fe-B magnetic tunnel junctions depending on the annealing temperature and the interface treatment

TL;DR

This study investigates how annealing temperature and interface treatments affect the sign and magnitude of tunnel magnetoresistance in Fe3O4/MgO/Co-Fe-B magnetic tunnel junctions, revealing Mg interdiffusion as a key factor.

Contribution

It demonstrates the impact of annealing temperature and interface treatments on TMR sign change and performance in Fe3O4-based MTJs, highlighting Mg interdiffusion effects.

Findings

TMR sign changes after annealing at 200-280°C.

Maximum TMR of -12% achieved with specific treatments.

Mg interdiffusion influences TMR behavior.

Abstract

Magnetite (Fe3O4) is an eligible candidate for magnetic tunnel junctions (MTJs) since it shows a high spin polarization at the Fermi level as well as a high Curie temperature of 585{\deg}C. In this study, Fe3O4/MgO/Co-Fe-B MTJs were manufactured. A sign change in the TMR is observed after annealing the MTJs at temperatures between 200{\deg}C and 280{\deg}C. Our findings suggest an Mg interdiffusion from the MgO barrier into the Fe3O4 as the reason for the change of the TMR. Additionally, different treatments of the magnetite interface (argon bombardment, annealing at 200{\deg}C in oxygen atmosphere) during the preparation of the MTJs have been studied regarding their effect on the performance of the MTJs. A maximum TMR of up to -12% could be observed using both argon bombardment and annealing in oxygen atmosphere, despite exposing the magnetite surface to atmospheric conditions before the deposition of the MgO barrier.