title: Magnetic interactions in the Zn-Co-O system: tuning local structure, valence and carrier type from extremely Co doped ZnO to ZnCo2O4.
abstract: We have investigated the relation between local structure, valence and carrier type with magnetism in the Zn-Co-O system. Thin films ranging from wurtzite Zn(1-x)Co(x)O (Co:ZnO) to ZnCo2O4 spinel were grown on c-sapphire substrates. On the one hand, the unprecedented doping of x = 0.6 Co in ZnO enables to study the structural and magnetic properties well-above the coalescence limit. On the other hand, the ZnCo2O4 spinel provides a p-type environment. We find a strong correlation between local structure, valence and carrier type throughout the Zn-Co-O system. In contrast to earlier publications neither 60% Co:ZnO nor ZnCo2O4 exhibit any sign of ferromagnetic order despite of the high concentration of magnetic ions and a p-type carrier background. Instead, antiferromagnetic exchange is found to be the predominant magnetic interaction in the Zn-Co-O system.
authors.affiliation: Institut für Halbleiter- und Festkörperphysik, Johannes Kepler Universität, Altenberger Str. 69, 4040 Linz, Austria.
authors.forename: Bastian
authors.initials: B
authors.lastname: Henne
authors.affiliation: Institut für Halbleiter- und Festkörperphysik, Johannes Kepler Universität, Altenberger Str. 69, 4040 Linz, Austria.
authors.forename: Verena
authors.initials: V
authors.lastname: Ney
authors.affiliation: ESRF-The European Synchrotron CS40220, 38043 Grenoble Cedex 9, France.
authors.forename: Katharina
authors.initials: K
authors.lastname: Ollefs
authors.affiliation: ESRF-The European Synchrotron CS40220, 38043 Grenoble Cedex 9, France.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Wilhelm
authors.affiliation: ESRF-The European Synchrotron CS40220, 38043 Grenoble Cedex 9, France.
authors.forename: Andrei
authors.initials: A
authors.lastname: Rogalev
authors.affiliation: Institut für Halbleiter- und Festkörperphysik, Johannes Kepler Universität, Altenberger Str. 69, 4040 Linz, Austria.
authors.forename: Andreas
authors.initials: A
authors.lastname: Ney