Regensburg 2007 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 27: II-VI semiconductors

HL 27.6: Talk

Wednesday, March 28, 2007, 15:30–15:45, H13

Spin polarization in Zn_0.95Co_0.05O:(Al,Cu) thin films — •Lars Hartmann, Qingyu Xu, Heidemarie Schmidt, Holger Hochmuth, Michael Lorenz, Chris Sturm, Christoph Meinecke, Annette Setzer, Pablo Esquinazi, and Marius Grundmann — Universität Leipzig, Fakultät für Physik und Geowissenschaften, Institut für Experimentelle Physik II, Linnéstrasse 5, D-04103 Leipzig, Germany

ZnCoO:Al, ZnCoO:(Al,Cu), and reference samples without Co have been grown by pulsed laser deposition to investigate the influence of Co-dopants and Cu-codopants on the magneto transport properties of ZnO. Positive magnetoresistance (MR) and anomalous Hall effect (AHE) have been observed for ZnCoO:(Al,Cu). Negative MR was observed in the Cu-codoped ZnO reference sample without Co [1]. Spin dependent scattering by isolated magnetic Cu impurities causes the observed negative MR in the reference sample [2]. The modeling of negative MR yields an electron spin polarization of 42% at 5 K and a Curie temperature T_C of 45 K. Possibly due to the complete ionization of intrinsic donors or Al donors in ZnO, above 50 K the MR is dramatically reduced. We also observed clear AHE in the Cu-codoped ZnCoO thin film. The AHE cannot be observed in ZnCoO without Cu-codopants. The observed temperature dependence of positive MR and magnetization hints towards a direct dependence of both effects. The simulation and understanding of the positive MR will provide key information for the enhancement of the intrinsic magnetization.

[1]L. Hartmann et al., J. Phys. D: Appl. Phys. 39 (2006). [2]M. Csontos et. al, Phys. Rev. Lett. 95 (2005).