Abstract
We have used an electron holography (EH) technique to directly probe the potential profile of tunnel barriers in magnetic tunnel junctions (MTJs). Barriers with under-, optimum-, or over-oxidized condition have been investigated. One important finding is that there is always slight oxidation of the top electrode because of film morphology. Sharp interfaces can be achieved in the bottom interface of optimally oxidized barrier or both interfaces in MTJs with under-oxidized barriers. We also demonstrate, theoretically and experimentally, how barrier shape affects the bias dependence and, in low barrier height case, result in inversed tunneling magnetoresistance (TMR) at high bias. The mechanism is very different from that responsible for inversed TMR in all biases. The finding leads to the possibilities of achieving better signals at high bias in real applications.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
T. Zhu, X.H. Xiang, G. Landry, D.V. Dimitrov, N. Garcia, and J.Q. Xiao, Phys. Rev. B 66, 94423 (2002).
X.H. Xiang, T. Zhu, G. Landry, J. Du, Y.W. Zhao, and J.Q. Xiao, Appl. Phys. Lett. 83, 2826 (2003).
J.G. Simmons, J. Appl. Phys. 34, 1793 (1963).
W.F. Brinkman, R.C. Dynes, and J.M. Rowell, J. Appl. Phys. 41, 1915 (1970).
J.S. Moodera and G. Mathon, J. Magn. Magn. Mater. 200, 248 (1999).
S.S.P. Parkin et al., J. Appl. Phys. 85, 5828 (1999).
J. Du, X.H. Xiang, G. Landry, B. You, H.W. Zhao, A. Hu, and J.Q. Xiao, J. Appl. Phys. 91, 8780 (2002).
J.M. De Teresa, A. Barthelemy, A. Fert, J.P. Contour, F. Montaigne, and P. Seneor, Science 286, 507 (1999).
A. Gupta, X.W. Li, and G. Xiao, J. Appl. Phys. 87, 6073 (2000).
M. Sharma, S.X. Wang, and J.H. Nickel, Phys. Rev. Lett. 82, 616 (1999).
M. Jullière, Phys. Lett. 54, 225 (1975).
E. Voelkl, L. Allard, and D. Joy, Introduction to Electron Holography (New York: Plenum, 1999), pp. 267–293, and references therein.
E. Voelkl, L. Allard, and D. Joy, Introduction to Electron Holography (New York: Plenum, 1999), p. 50.
G. Landry, X.H. Xiang, Y. Dong, and J.Q. Xiao, Appl. Phys. Lett. 78, 501 (2001).
D.R. Lide, CRC Handbook of Chemistry and Physics, 2000–2001 (Boca Raton, FL: CRC Press, 2000), p. 75.
P.C. van Son, H. van Kempen, and P. Wyder, Phys. Rev. Lett. 58, 2271 (1987).
X.H. Xiang, T. Zhu, J. Du, G. Landy, and J.Q. Xiao, Phys. Rev. B 66, 174407 (2002).
G.V. Samsonov, The Oxide Handbook (New York: Plenum, 1982), p. 214.
J.G. Wang, P.P. Freitas, E. Snoeck, P. Wei, and J.C. Soares, Appl. Phys. Lett. 79, 4387 (2001).
F.F. Li, Z.Z. Li, M.W. Xiao, J. Du, W. Xu, and A. Hu, Phys. Rev. B 69, 054410 (2004).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Sheng, WT., Wang, W.G., Xiang, X.H. et al. Probing tunnel barrier shape and its effects on inversed tunneling magnetoresistance at high bias. J. Electron. Mater. 33, 1274–1279 (2004). https://doi.org/10.1007/s11664-004-0153-3
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/s11664-004-0153-3