Spintronics in semiconductor nanostructures

In recent years several experiments have successfully demonstrated spin injection into semiconductors. All of these used concepts where the sign of the spin polarization is determined by a magnetic field. In resonant tunneling diodes with semimagnetic semiconductor layers, spin selection can be obtained by changing the applied voltage. In this paper we give a brief explanation for the necessity of spin filters and present first results which demonstrate a giant spin-splitting in an all II-VI semiconductor resonant tunneling diode. Moreover, we present transport experiments performed on ferromagnetic (Ga,Mn)As nanoconstrictions that can be used to trap and investigate domain walls. When operated in the tunneling regime, these constrictions can show a magnetoresistance of up to 2000%. (C) 2004 Elsevier B.V. All rights reserved.