Defect induced low temperature ferromagnetism in Zn{sub 1-x}Co{sub x}O films

Journal Article · Sun Apr 01 04:00:00 EDT 2007 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.2713935· OSTI ID:20982802

Biegger, E; Fonin, M; Ruediger, U; Janssen, N; Beyer, M; Thomay, T; Bratschitsch, R; Dedkov, Yu S ^[1]

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1. Fachbereich Physik, Universitaet Konstanz, 78457 Konstanz (Germany)

We present a detailed study on the structural, magnetic, and optical properties, as well as the electronic structure of epitaxial Co-doped ZnO films prepared by magnetron sputtering. Different preparation conditions were implemented in order to control the concentration of oxygen vacancies in the ZnO host lattice. Magnetization measurements indicate ferromagnetic behavior at low temperature for samples prepared at oxygen-poor conditions whereas the samples prepared at oxygen-rich conditions show extremely small ferromagnetic signal corroborating that ferromagnetism in Zn{sub 1-x}Co{sub x}O correlates with the presence of the oxygen-related defects. X-ray absorption spectroscopy (XAS) at the Co L{sub 2,3} edge together with optical transmittance measurements show that Co ions are present in the high-spin Co{sup 2+} (d{sup 7}) state under tetrahedral symmetry indicating a proper incorporation in the ZnO host lattice. Comparison of the O K edge XAS spectra of the samples prepared at different conditions show substantial changes in the spectral line shape which are attributed to the presence of lattice defects such as oxygen vacancies in the ferromagnetic oxygen-poor Co-doped ZnO samples. Our findings indicate that the ferromagnetic properties of Co-doped ZnO samples are strongly correlated with the presence of oxygen vacancies in the ZnO lattice supporting the spin-split impurity band model.

• OSTI ID: 20982802
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 7 Vol. 101; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ABSORPTION SPECTROSCOPY
COBALT
COBALT IONS
DEPOSITION
DOPED MATERIALS
ELECTRONIC STRUCTURE
EPITAXY
FERROMAGNETIC MATERIALS
FERROMAGNETISM
MAGNETIZATION
OPTICAL PROPERTIES
OXYGEN
SEMICONDUCTOR MATERIALS
SPIN
SPUTTERING
THIN FILMS
VACANCIES
X-RAY SPECTRA
X-RAY SPECTROSCOPY
ZINC OXIDES