Regensburg 2007 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 45: ZnO II

HL 45.3: Talk

Thursday, March 29, 2007, 14:30–14:45, H17

Magnetoresistance in n-type conducting magnetic ZnO films — •Qingyu Xu, Lars Hartmann, Heidemarie Schmidt, Holger Hochmuth, Michael Lorenz, and Marius Grundmann — Universität Leipzig, Fakultät für Physik und Geowissenschaften, Institut für Experimentelle Physik II, Linnéstrasse 5, D-04103 Leipzig, Germany

The magnetoresistance (MR) of differently alloyed, n-type conducting ZnO films (Co, Mn, Ti, Cu, Nd) prepared by pulsed laser deposition (PLD) on a-plane sapphire substrates in oxygen atmosphere was probed in the temperature range from 5 K to 290 K with magnetic fields up to 6 T. At 5 K, large positive MR was observed in Co [1] and Mn doped ZnO films, while large negative MR was observed in Ti, Cu [2], and Nd doped ZnO films. The positive MR in doped ZnO was attributed to a giant spin splitting enhanced by s-d exchange interactions. This will affect considerably quantum corrections to the conductivity associated with the disorder modified electron-electron interactions [3]. The probed positive MR reveals that the s-d exchange interaction is strong in Co and Mn doped ZnO. Weak s-d exchange interaction has been observed in Ti, Cu, and Nd doped ZnO. Except for the Cu-doped ZnO, these results agree with magnetic circular dichroism results [4]. The positive and negative MR decreases drastically with increasing temperature, being nearly neglectable above 100 K. [1] Q. Xu, et al, Phys. Rev. B 73, 205342 (2006). [2] L. Hartmann, et al, J. Phys. D: Appl. Phys., in press. [3] T. Andrearczyk, et al, Phys. Rev. B 72, 121309(R) (2005). [4] K. Ando, et al, J. Appl. Phys. 89, 7284 (2001).