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HL: Fachverband Halbleiterphysik

HL 47: Spintronics (organized by MA)

HL 47.5: Vortrag

Dienstag, 1. April 2014, 14:45–15:00, HSZ 401

Magnetic anisotropy in CoFe/MgO/CoFe magnetic tunnel junctions with ultrathin electrode layers and its composition dependence — •Jia Zhang, Christian Franz, Michael Czerner, and Christian Heiliger — I. Physikalisches Institut, Justus Liebig University, Giessen, Germany

MgO based magnetic tunnel junctions (MTJs) with ultrathin CoFeB magnetic electrodes can have perpendicular magnetic anisotropy and a low switching current. In addition, MgO-MTJs with perpendicular anisotropy may also be easier to switch by thermal spin transfer torque and may pave its potential application in Spincaloritronics. In this talk, the magnetic anisotropy in CoFe/MgO/CoFe-MTJs on different substrates for instance Cu, Au, MgO etc. and different CoFe alloy composition are discussed using full relativistic Korringa-Kohn-Rostoker and coherent potential approximation (CPA) first-principles calculations. The magnetic anisotropy energy (MAE) in CoFe/MgO/CoFe-MTJs was calculated by employing magnetic force theory. The calculated MAE in Co_xFe_1−x/MgO/Co_xFe_1−x-MTJs decreased with the increasing of Co composition. The d_zx(d_yz) and d_xy(d_x²−y²) orbital and its evolution in the spin down channel was found to be responsible for the rise of magnetic anisotropy and the composition dependence. The shape anisotropy energy was also calculated and thus the phase diagram with perpendicular anisotropy versus composition and thickness was determined. Finally, we will give a brief discussion on magneto resistance and spin-transfer torque in CoFe/MgO/CoFe-MTJs with perpendicular easy axis.