Effect of oxygen vacancies on interlayer exchange coupling in Fe/MgO/Fe tunnel junctions

Authors

Mikhail Ye Zhuravlev, University of Nebraska-LincolnFollow
Julian P. Velev, University of Nebraska-LincolnFollow
A. V. Vedyayev, Department of Physics, M.V. Lomonosov Moscow State University, 119899 Moscow, Russian Federation
Evgeny Y. Tsymbal, University of Nebraska-LincolnFollow

Date of this Version

5-1-2006

Comments

Published in Journal of Magnetism and Magnetic Materials 300:1 (May 2006), pp. e277-e280; doi:10.1016/j.jmmm.2005.10.099. Copyright © 2005 Elsevier B.V. Used by permission. http://www.sciencedirect.com/science/journal/03048853

Abstract

We have investigated the interlayer exchange coupling (IEC) in Fe/MgO/Fe(0 0 1) tunnel junctions with and without oxygen vacancies in MgO, using model and density functional calculations. The model predicts that IEC changes sign from ferromagnetic to antiferromagnetic if a defect level matches the Fermi energy. Ab initio calculations show that for perfect junctions, IEC is ferromagnetic and decreases exponentially with MgO thickness. Oxygen vacancies placed in the middle of MgO make IEC antiferromagnetic for three monolayers (MLs) of MgO, but do not change the sign of IEC for five MLs. The latter fact is explained within the model, which suggests that for the impurity level lying below the Fermi energy IEC can change sign with increasing barrier thickness due to the weaker coupling of the impurity level to the ferromagnets.