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 Gross1 — 1Walther-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).