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MA: Fachverband Magnetismus

MA 5: Spindependent Transportphenomena I

MA 5.7: Talk

Monday, February 25, 2008, 11:45–12:00, H 0112

Reduction of the tunnel magnetoresistance in Fe/MgO/Fe by disorder — •Peter Bose¹, Jürgen Henk², and Ingrid Mertig¹ — ¹Martin Luther University Halle-Wittenberg, Halle, Germany — ²Max Planck Institute of Microstructure Physics, Halle, Germany

Spin-dependent ballistic transport is usually computed for ideal tunnel junctions, leading to magnetoresistance (MR) ratios much larger than their experimental counterparts. Disorder at the interfaces is believed to reduce the MR ratios considerably. A proof of this assumption is hardly possible in experiments and very demanding for ab initio transport theory.

We report on a theoretical investigation of the MR in Fe/FeO/MgO/Fe junctions with substitutional disorder. In particular, partially occupied O sites in the FeO layer—as found in experiments [1]—are addressed. Within our layer-KKR approach to Landauer-Büttiker theory, a supercell method is implemented and applied for selected O concentrations.

The MR ratio is significantly reduced for the disordered samples, thus improving essentially the agreement with experimental results. The decomposition of the conductance into a specular and a diffusive contribution allows to discuss the transport properties in detail.

[1] C. Tusche et al., Phys. Rev. Lett. 95 (2005) 176101.