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°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°C and 280°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°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.
Highlights
Sign change in the tunnel magnetoresistance of Fe3O4/MgO/Co-Fe-B magnetic tunnel junctions depending on the annealing temperature and the interface treatment
A sign change in the tunnel magnetoresistance (TMR) is observed after annealing the magnetic tunnel junctions (MTJs) at temperatures between 200◦C and 280◦C
Our findings suggest an Mg interdiffusion from the MgO barrier into the Fe3O4 as the reason for the change of the TMR
Summary
A central device for this application is the magnetic tunnel junction, MTJ.2 It consists of two ferromagnetic conductors separated by a very thin insulating tunneling barrier. The resistance across this device depends on the relative orientation of the magnetization of the ferromagnetic electrodes, which leads to two different states: The magnetization of both electrodes can be parallel or antiparallel. This tunnel magnetoresistance (TMR) was first observed by Julliere et al. in
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