TY - JOUR
T1 - Extended solubility of CoO in ZnO and effects on magnetic properties
AU - Schaedler, Tobias A.
AU - Gandhi, Ashutosh S.
AU - Saito, Mitsuhiro
AU - Rühle, Manfred
AU - Gambino, Richard
AU - Levi, Carlos G.
N1 - Funding Information:
This investigation was supported through a seed project from the UCSB Materials Research Laboratory, NSF-MRSEC award No. DMR00-80034. The Max Planck Gesellschaft provided support for the activities at Max-Planck-Institut für Metallforschung (MPI-MF), including an extended research visit by T.S. under the collaborative MPG/UCSB agreement. Additional travel support for T.S. was provided by the UCSB International Center for Materials Research. Support for R.G. was provided by the Center on Thermal Spray Research, NSF MRSEC Award No. DMR 0080021. The authors would like to thank Professors D.R. Clarke, N. Spaldin, and F.F. Lange as well as Dr. S. Krämer (UCSB) for enlightening discussions, Dr. J. O’Brien (Quantum Design, San Diego, CA) for performing the magnetic measurements, Dr. O. Fabrichnaya (MPI-MF) for providing thermodynamic data, and K. Hahn and Dr. S. Sturm (MPI-MF) for assistance with the TEM characterization.
PY - 2006/3
Y1 - 2006/3
N2 - The metastable solid solubility extension of CoO in ZnO (wurtzite) was investigated in precursor-derived powders as well as in thin films grown on sapphire substrates by pulsed laser deposition. A maximum solubility of 30% Co2+ in ZnO was achieved in the powders. Transmission electron microscopy (TEM) of the films revealed them to have grown epitaxially and retained up to nearly 40% CoO in solid solution, but some Co2+ precipitated as rock-salt. The temperature dependence of the metastable solubility limit in the ZnO-CoO system was assessed and is discussed in terms of the relevant thermodynamic factors. The magnetic properties of n-type conductive Zn0.79 Co0.2Al0.01O films were studied, yielding evidence of a ferromagnetic phase with a TC of 25 K and a second, magnetically ordered, phase with positive exchange and arguably a TC of ∼250 K. Connections between the properties and microstructural observations in high resolution TEM are proposed.
AB - The metastable solid solubility extension of CoO in ZnO (wurtzite) was investigated in precursor-derived powders as well as in thin films grown on sapphire substrates by pulsed laser deposition. A maximum solubility of 30% Co2+ in ZnO was achieved in the powders. Transmission electron microscopy (TEM) of the films revealed them to have grown epitaxially and retained up to nearly 40% CoO in solid solution, but some Co2+ precipitated as rock-salt. The temperature dependence of the metastable solubility limit in the ZnO-CoO system was assessed and is discussed in terms of the relevant thermodynamic factors. The magnetic properties of n-type conductive Zn0.79 Co0.2Al0.01O films were studied, yielding evidence of a ferromagnetic phase with a TC of 25 K and a second, magnetically ordered, phase with positive exchange and arguably a TC of ∼250 K. Connections between the properties and microstructural observations in high resolution TEM are proposed.
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U2 - 10.1557/jmr.2006.0092
DO - 10.1557/jmr.2006.0092
M3 - Article
AN - SCOPUS:33645101926
SN - 0884-2914
VL - 21
SP - 791
EP - 801
JO - Journal of Materials Research
JF - Journal of Materials Research
IS - 3
ER -