Berlin 2005 – scientific programme
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HL: Halbleiterphysik
HL 10: Spintronik II
HL 10.5: Talk
Friday, March 4, 2005, 16:00–16:15, TU P270
Local carrier induced ferromagnetisms in a II-VI dilute magnetic semiconductor. — •Charles Gould1, Anatoliy Slobodskyy1, Pawel Hawrylak2, Fanyao Qu2, Taras Slobodskyy1, Peter Grabs1, Daniel Supp1, Georg Schmidt1, and Laurens Molenkamp1 — 1Universität Würzburg (EP3), Am Hubland, D-97074, Würzburg, Germany — 2Institute for Microstructural Sciences, National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada
We present transport measurements on an all-II-VI semiconductor tunneling structure consisting of a ZnBeMnSe barrier embedded with CdSe self assembled quantum dots. The zero magnetic field I-V characteristic exhibits many resonant peaks which are identified with tunneling through individual quantum dots. When a magnetic field is applied, the resonant peaks split following the Brillouin-like giant Zeeman splitting of the barrier. Given that there is no Mn in the dots, and the effect of the giant Zeeman splitting on the barrier height has negligible effect on peak position, this confirms that the individual electron levels in the quantum dots couple to the Mn system in the barrier.
More surprising is the observation that the splitting between pairs of states of opposite spin remains finite in the absence of magnetic field. This is explained by in a model taking into account both the antiferromagnetic direct Mn-Mn coupling and the carrier mediate ferromagnetic interaction caused by the presence of unpaired electron spins in the dot. The model confirms that the carriers in our system induce a local ferromagnetic interaction of the Mn ions in the vicinity of the current carrying dot.