Dresden 2003 – scientific programme

Parts | Days | Selection | Search | Downloads | Help

HL: Halbleiterphysik

HL 32: Spinabh
ängiger Transport II

HL 32.8: Talk

Wednesday, March 26, 2003, 16:15–16:30, POT/81

EPR and Ferromagnetism in Diluted Magnetic Semiconductor Quantum Wells — •Jürgen König¹ and Allan MacDonald² — ¹Institut für Theoretische Festkörperphysik, Universität Karlsruhe — ²Department of Physics, University of Texas at Austin, USA

We develop a theory of collective spin excitations in quasi-two-dimensional diluted magnetic semiconductor quantum wells. Our theory is able to explain the anomalously large Knight shift observed in recent electron paramagnetic resonance (EPR) experiments. We use our theory to address the physics of ferromagnetism in n-type diluted magnetic semiconductor quantum-well systems, which has not yet been observed. We point out that spin-orbit interactions are necessary to support ferromagnetism, predict ferromagnetic transition temperatures in symmetric quantum wells that can be well below those implied by mean-field theory, and suggest that the crossover from collective-fluctuation-limited to mean-field-interaction-limited ferromagnetism can be observed in these systems by using a bias voltage to adjust the spin-orbit interaction strength.