Berlin 2008 – scientific programme

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MA: Fachverband Magnetismus

MA 23: Spinelectronics/ Spininjection in Heterostructures

MA 23.2: Talk

Wednesday, February 27, 2008, 17:00–17:15, H 1028

Electrical spin injection from Fe into Si(001): ab-initio calculations — •Phivos Mavropoulos and Stefan Blügel — IFF, Forschungszentrum Jülich, D-52425 Jülich, Germany

Electrical spin injection is highly important for novel spintronics devices. Recent experiments [1] have demonstrated efficient spin injection from Fe into Si with very large spin coherence length of the injected current. In the present contribution we seek a theoretical upper limit for the injection efficiency in Fe/Si(001) junctions. Our calculations of the electronic structure and spin-dependent transport are based on the Korringa-Kohn-Rostoker Green function method [2] within local density functional theory. We show that use of slightly strained Si [3] along the growth axis lifts the degeneracy of the Si conduction band, so that only symmetry-selected Δ₁ states at the center of the surface Brillouin zone carry current. States of such symmetry are absent from the minority-spin bands of Fe at the Fermi level. As a result, the interface allows only spin-selective transmission, allowing in for a high current polarization. We discuss complications arising from interface resonances formed in the minority-spin bands, which reduce the transmission efficiency by resonant tunneling through the Schottky barrier, and we address the problem of reduction of the Fe interface moment when it is strained to match the Si lattice parameter.

[1] B.T. Jonker et at., Nature Physics 3, 542 (2007).

[2] P. Mavropoulos, N. Papanikolaou, and P.H. Dederichs, Phys. Rev. B 69, 125104 (2004).

[3] D. Buca et al., Appl. Phys. Lett. 90, 032108 (2007).