Dresden 2006 – scientific programme

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MA: Magnetismus

MA 3: Spin-Dependent Transport Phenomena I

MA 3.10: Talk

Monday, March 27, 2006, 12:30–12:45, HSZ 103

Induced magnetic anisotropy effects on the transport properties of magnetic tunnel junctions — •Voicu Popescu and Hubert Ebert — Department Chemie/Physikalische Chemie, University of Munich, Butenandtstr. 5-13, 81377 Munich, Germany

We report results of calculations on the electronic, magnetic and transport properties of Fe/GaAs/Fe and Fe/GaAs/Au/Fe magnetic tunneling junctions (MTJs) that have been obtained using the tight-binding Korringa-Kohn-Rostoker Green function method in a spin-polarised fully relativistic formulation (TB-SPR-KKR). This approach, by coupling the electron spin and orbital degrees of freedom, allows one to properly account for the changes induced in the electronic transport when different magnetic configurations, e.g., in-plane and out-of-plane, are considered.

Recent experimental work on MTJs based on diluted magnetic semiconductors have shown that, while keeping the orientation of the magnetisation in the plane of the junction but varying its azimuthal angle, a measurable dependence of the resistance with respect to this angle can be observed. This phenomenon is now commonly termed as Tunneling Anisotropic Magnetoresistance (TAMR).

We have performed analogous theoretical investigations on MTJs based on metallic (ferromagnetic or non-magnetic) leads. Our results show that a similar dependence is obtained also for such systems and it can be related to the spin-orbit coupling induced magnetic anisotropy at the metal/semiconductor interface. This, in turn, is shown to vary for different terminations (As or Ga) of the semiconductor, revealing the role of the covalent bonding at the interface.