Dresden 2006 – scientific programme

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MA: Magnetismus

MA 20: Poster: Films(1-36) Transp(37-56) Ex.Bias(57-67) Spindyn(68-80) Micromag(81-95) Particle(96-109) Imag.+Surface(110-113) Spinelectr(114-122) Theory+Micromag(123-131) Spinstr+Aniso(132-142) MagMat(143-156) Meas(157,158) MolMag+Kondo(159-162) Postdead(163-)

MA 20.43: Poster

Tuesday, March 28, 2006, 15:15–19:15, P1

How does the interface structure influence the thickness dependence of tunneling magnetoresistance? — •Christian Heiliger, Peter Zahn, Bogdan Yu. Yavorsky, and Ingrid Mertig — Martin Luther University, FB Physik, FG Theorie, D-06099 Halle, Germany

New experiments [1-3] based on epitaxially grown Fe/MgO/Fe samples obtained TMR ratios which exceed the predictions by Julliere’s model. In addition an oscillating behaviour of the tunneling magnetoresistance (TMR) depending on the barrier thickness was found [1].

The aim of our work is to demonstrate the influence of different interface geometries on the thickness dependence of the TMR ratio. Three different interface configurations deduced from experiments have been considered [4]. A screened Korringa-Kohn-Rostoker (KKR) method based on density functional theory was applied to calculate the electronic and magnetic structure of the different junctions self-consistently. The Landauer conductance of planar junctions was calculated using the Baranger-Stone scheme by means of Green’s functions in the limit of coherent tunneling.

Positive and negative TMR ratios are obtained as a function of interface structure and bias voltage. The results demonstrate that the IV-characteristic is determined by the interface structure independent on the barrier thickness.

[1] S. Yuasa et al., Nature Materials 3, 868 (2004)

[2] J. Faure-Vincent et al., Appl. Phys. Lett. 82, 4507 (2003)

[3] S.S.P. Parkin et al., Nature Materials 3, 862 (2004)

[4] C. Heiliger et al., Phys. Rev. B accepted