Berlin 2005 – scientific programme

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HL: Halbleiterphysik

HL 23: II-VI Halbleiter II

HL 23.1: Talk

Saturday, March 5, 2005, 10:45–11:00, TU P-N202

EPR study on the valence state of 3d transition-metal ions in ZnO based diluted magnetic semiconductors — •Mariana Diaconu, Heidemarie Schmidt, Andreas Pöppl, Rolf Böttcher, Joachim Höntsch, Holger Hochmuth, Michael Lorenz, and Marius Grundmann — Institut für Experimentelle Physik II, Fakultät für Physik und Geowissenschaften, Universität Leipzig, Linnéstrasse 3-5, 04103 Leipzig, Germany

In this paper we discuss theoretical and experimental results of electron paramagnetic resonance (EPR) for 3d transition-metal (TM) doped ZnO films, system belonging to a new class of materials called diluted magnetic semiconductors (DMS). Ferromagnetism at room-temperature was found on DMS, for example on Mn-alloyed ZnO films grown by pulsed laser deposition (PLD) [1,2]. For explaining the physical origin of the observed ferromagnetism, the valence state of 3d TM ions in ZnO has to be known.

For Mn-doped ZnO we performed EPR measurements on films obtained by PLD with Mn concentrations ranging from 0.1 to 10 at%. We observed the typical Mn²⁺ spectrum for low doping (0.1 at% Mn). For higher Mn-concentrations the hyperfine lines are not visible, but we see the fine-structure lines, broadened by dipole-dipole interactions. Onto these lines an intense broad single line was superposed. The broad single line, also found in Mn-alloyed nanostructures, is due to Mn ions in higher local concentrations. We modelled the EPR spectra and obtained the fine and hyperfine splitting parameters of Mn-alloyed ZnO.

[1] P. Sharma et al., Nature Materials 2 (2003), 673.

[2] M. Diaconu et al., submitted to Phys. Rev. B.