Regensburg 2004 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 49: Spinabh
ängiger Transport III

HL 49.3: Vortrag

Freitag, 12. März 2004, 11:30–11:45, H13

Magnetic moment induced by spin-polarized currents in a semiconductor heterostructure — •Frank Lehmann, Charles Gould, Christian Rüster, Peter Grabs, Georg Schmidt, and Laurens W. Molenkamp — Unversität Würzburg, Physikalisches Institut (EP 3), Am Hubland, D-97974 Würzburg, Germany

In recent years, several experiments have successfully demonstrated the electrical injection of spin-polarized currents into semiconductors. These experiments are sensitive to the polarization of the current but not to the magnetic moment induced by the spin-polarized carriers. We have now successfully performed SQUID experiments that provide direct evidence of a current induced magnetization in an electrical spin injection device.

The magnetic moment of a ZnBeMnSe/GaAs heterostructure was measured using a SQUID magnetometer and lock-in technique at various magnetic fields, currents, and temperatures. When the background magnetic moment that results from Biot-Savart‘s law is eliminated, we observe a clear change in the magnetic moment at the field and current configurations for which spin injecton is expected. The field and temperature dependence show that the effect is related to the magnetization of the DMS. We interpret our results in terms of (i) the band bending that occurs in the DMS at higher eletric fields and that reduces the spin-polarization in the magnetic material and (ii) spin accumulation in the GaAs.