Regensburg 2010 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 24: Spinelectronics / Spin Injection in Heterostructures

MA 24.2: Vortrag

Donnerstag, 25. März 2010, 10:30–10:45, H22

Spin Injection and Extraction in Fe/GaAs — •Bernhard Endres, Frank Hoffmann, Dieter Schuh, Georg Woltersdorf, Christian Back, and Günther Bayreuther — Universität Regensburg, Institut für Experimentelle und Angewandte Physik

Majority spin injection into GaAs(001) has recently been observed from Fe [1] and FeCo [2] epitaxial contacts. Consequently, minority polarization is expected in the semiconductor when the tunneling current is reversed from electron injection to extraction. This was clearly observed for FeCo contacts [2], but a complex bias dependence of the spin polarization was found in the case of Fe contacts changing from sample to sample [1]. In order to find out whether this discrepancy originates from a different band filling in the two materials or from specific interface properties, the GaAs structure [2] and an epitaxial Fe contact layer were grown in two connected MBE chambers without breaking the vacuum. After lithographic patterning the spin polarization in the GaAs, P_n, was measured by MOKE across a cleaved edge as described in ref. 2. P_n as a function of magnetic field reproduces the switching behavior of the Fe contact. The bias dependence of P_n showed the same sign reversal as previously seen for FeCo [2] in contrast to the behavior found in ref. 1. This rules out the material-specific band structure to be the origin of previous contrasting results, and it indicates that spin injection is crucially affected by interface properties like Schottky barrier profile or interfacial bands which in turn depend on the specific growth conditions. [1] X. Lou et al., Nature Phys. 3, 197 (2007); [2] P. Kotissek et al., Nature Phys. 3, 872 (2007)