Regensburg 2002 – wissenschaftliches Programm

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SYSP: Spintronics in Grundlagen und Anwendungen

SYSP III: HV III

SYSP III.1: Hauptvortrag

Donnerstag, 14. März 2002, 10:30–11:00, H1

The physics of spin injection — •Georg Schmidt and Laurens W. Molenkamp — Physikalisches Institut, Universität Würzburg, Am Hubland, 97074 Würzburg

Recently, we used a paramagnetic dilute magnetic semiconductor (DMS) to demonstrate robust spin-injection into a semiconductor LED structure. We have now demonstrated a new magnetoresistance effect which is based on spin-injection from a similar DMS into non magnetic ZnBeSe. The effect is a large positive magnetoresistance which occurs due to the suppression of one of the two spin channels in the non magnetic semiconductor and can be regarded as the paramagnetic analogue to GMR. Results up to now show an effect of ΔR/R=25%, but the theoretical upper limit is 100%. The magnetoresistance effect shows a strong temperature dependence which can be explained by the distribution of the electrons in the spin-up and spin-down level respectively. Besides the temperature dependence we also observe a strong dependence of the magnitude of the effect on the applied voltage. When going away from linear response, we find that the magnetoresistance disappears, an effect which can be explained by spin accumulation effects at the interface. Besides the experimental results and possible explanations, alternative concepts for spin injection into semiconductors like tunnel barriers or ballistic transport will also be discussed.