Interface Science

, Volume 12, Issue 1, pp 105–116 | Cite as

Metal-Oxide Interfaces in Magnetic Tunnel Junctions

  • I.I. Oleynik
  • E.Y. Tsymbal


Metal-oxide interfaces play an important role in spintronics—a new area of microelectronics that exploits spin of electrons in addition to the traditional charge degree of freedom to enhance the performance of existing semiconductor devices. Magnetic tunnel junctions (MTJs) consisting of spin-polarized ferromagnetic electrodes sandwiching an insulating barrier are such promising candidates of spintronic devices. The paper reviews recent results of first-principle density-functional studies of the atomic and electronic structure of metal-oxide interfaces in Co/Al2O3/Co and Co/SrTiO3/Co MTJs. The most stable interface structures, O-terminated for fcc Co (111)/α-alumina(0001) and TiO2-terminated with oxygens on top of Co atoms for fcc Co (001)/SrTiO3(001) were identified based on energetics of metal-oxide cohesion at the interface. The covalent character of bonding for both the Co/alumina and Co/SrTiO3 interface structures has been determined based on the pattern of electron distribution across the interface. The Al-terminated Co/alumina interface that corresponds to an under-oxidized MTJ exhibits a metallic character of bonding. The unusual charge transfer process coupled with exchange interactions of electrons in Co results in quenching of surface magnetism at the interface and substantial reduction of work of separation. The electronic structure of the O-terminated Co/Al2O3/Co MTJ exhibits negative spin polarization at the Fermi energy within the first few monolayers of alumina but it eventually becomes positive for distances beyond 10 Å. The Co/SrTiO3/Co MTJ shows an exchange coupling between the interface Co and Ti atoms mediated by oxygen, which results in an antiparallely aligned induced magnetic moment on Ti atoms. This may lead to a negative spin polarization of tunneling across the SrTiO3 barrier from the Co electrode. The results illustrate the important fact that spin-polarized tunneling in magnetic tunnel junctions is not determined entirely by bulk density of states of ferromagnet electrodes, but is also very sensitive to the nature of the insulating tunneling barrier, as well as the atomic structure and bonding at the ferromagnet/insulator interface.


Fermi Energy Electron Distribution Exchange Coupling Interface Structure Charge Transfer Process 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    S.A. Wolf, D.D. Awschalom, R.A. Buhrman, J.M. Daughton, S. von Molnar, M.L. Roukes, A.Y. Chtchelkanova, and D.M. Treger, Science 294, 488 (2001).Google Scholar
  2. 2.
    J.M. Slaughter, E.Y. Chen, R. Whig, B.N. Engel, J. Janesky, and S. Tehrani, JOM-e 52, 6 (2000).Google Scholar
  3. 3.
    J.S. Moodera, J. Nassar, and G. Mathon, Ann. Rev. Mater. Sci. 29, 381 (1999).Google Scholar
  4. 4.
    R. Meservey and P.M. Tedrow, Phys. Rep. 238, 173 (1994).Google Scholar
  5. 5.
    M. Julliere, Phys. Lett. A 54, 225 (1975).Google Scholar
  6. 6.
    J.M. De Teresa, A. Barthelemy, A. Fert, J.P. Contour, R. Lyonnet, F. Montaigne, P. Seneor, and A. Vaures, Phys. Rev. Lett. 82, 4288 (1999).Google Scholar
  7. 7.
    D.J. Monsma and S.S.P. Parkin, Appl. Phys. Lett. 77, 883 (2000).Google Scholar
  8. 8.
    I.I. Oleinik, E.Y. Tsymbal, and D.G. Pettifor, Phys. Rev. B 62, 3952 (2000).Google Scholar
  9. 9.
    I.I. Oleinik, E.Y. Tsymbal, and D.G. Pettifor, Phys. Rev. B 65, 020401 (2002).Google Scholar
  10. 10.
    I.G. Batyrev, A. Alavi, and M.W. Finnis, Phys. Rev. B 62, 4698 (2000).Google Scholar
  11. 11.
    M.C. Payne, M.P. Teter, D.C. Allan, T.A. Arias, and J.D. Joannopoulos, Rev. Mod. Phys. 64, 1045 (1992).Google Scholar
  12. 12.
    B. Hammer, L. B. Hansen, and J. K. NØrskov, Phys. Rev. B 59, 7413 (1999).Google Scholar
  13. 13.
    CRC Handbook of Chemistry and Physics (CRC Press, NY, 1996).Google Scholar
  14. 14.
    R. Phillips, J. Zou, A.E. Carlsson, and M. Widom, Phys. Rev. B 49, 9322 (1994).Google Scholar
  15. 15.
    T. Wagner, G. Richter, and M. Ruhle, J. Appl. Phys. 89, 2606 (2001).Google Scholar
  16. 16.
    T. Ochs, S. Kostlmeier, and C. Elsasser, Integr. Ferroelectr. 32, 959 (2001).Google Scholar
  17. 17.
    B. Holm, R. Ahuja, Y. Yourdshahyan, B. Johansson, and B.I. Lundqvist, Phys. Rev. B 59, 12777 (1999)Google Scholar
  18. 18.
    S.D. Mo and W.Y. Ching, Phys. Rev. B 57, 15219 (1998).Google Scholar
  19. 19.
    R.H. French. Am. Ceram. Soc. 73, 477 (1990).Google Scholar
  20. 20.
    J.C. Boetter, Phys. Rev. B 55, 750 (1997).Google Scholar
  21. 21.
    V.L. Moruzzi, J.F. Janak, and A.R. Williams, Calculated Electronic Properties of Metals (Pergamon, New York, 1978).Google Scholar
  22. 22.
    Y. Tezuka, S. Shin, and T. Ishii, J. Phys. Soc. Jpn. 63, 347 (1994).Google Scholar
  23. 23.
    R.D. King-Smith and D. Vanderbilt, Phys. Rev. B 49, 5828 (1994).Google Scholar
  24. 24.
    I.G. Batyrev, A. Alavi, and M.W. Finnis, Phys. Rev. Lett. 82, 1510 (1999).Google Scholar
  25. 25.
    J. Kanamori, J. Phys. Chem. Solids 10, 87 (1959).Google Scholar
  26. 26.
    J. Tersoff and D.R. Hamman, Phys. Rev. B 31, 805 (1985).Google Scholar
  27. 27.
    P. LeClair, J.T. Kohlhepp, H.J.M. Swagten, and W.J.M. de Jonge, Phys. Rev. Lett. 86, 1066 (2001).PubMedGoogle Scholar

Copyright information

© Kluwer Academic Publishers 2004

Authors and Affiliations

  1. 1.Department of PhysicsUniversity of South FloridaTampaUSA
  2. 2.Department of Physics and AstronomyUniversity of Nebraska-LincolnLincolnUSA

Personalised recommendations