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Dresden 2006 – scientific programme

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MA: Magnetismus

MA 25: Spin-Electronics I

MA 25.4: Talk

Thursday, March 30, 2006, 11:00–11:15, HSZ 103

Low temperature ferromagnetism in Co-doped ZnO due to hopping — •Karl-Wilhelm Nielsen1, Maike Luebbe1, Sebastian Bauer1, Juergen Simon2, Werner Mader2, Sebastian T. B. Goennenwein1, Matthias Opel1, and Rudolf Gross11Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching — 2Institut fuer Anorganische Chemie, Universitaet Bonn, 53177 Bonn

Transition-metal doped ZnO is a promising candidate for the realization of a diluted magnetic semiconductor. According to a model by Coey et al. [1], the ferromagnetism is mediated through an impurity band and Curie temperatures above room temperature can be expected.
We have fabricated homoepitaxial Co-doped ZnO thin films on ZnO substrates by pulsed laser deposition. The samples were grown in Ar atmosphere at different substrate temperatures to obtain various concentrations of oxygen vacancies. SQUID magnetometry and magnetotransport measurements showed clear ferromagnetic behavior below 50 K. Clusters as the source of ferromagnetism can be excluded by transmission electron microscopy.
Our detailed magneto-transport measurements show that correlated hopping in the oxygen vacancy band is essential for the ferromagnetic coupling. We critically compare these findings with the model of Coey et al. [1] and discuss the possibility of room temperature ferromagnetism.
This work is supported by the DFG via SPP 1157.

[1] J. M. D. Coey et al. Nature Materials 4 173 (2005).

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