Study on the Magnetism of Epitaxial ZnCoO Films Deposited by Pulsed Laser Deposition

doi:10.3724/SP.J.1077.2012.00369

Abstract

Abstract:

Zn_1-_xCo_xO films were deposited on Al₂O₃(001) substrates at different oxygen pressures with Zn_0.95Co_0.05O ceramic target by using pulsed laser deposition method. With X-ray diffraction (XRD), electron probe microanalysis (EPMA) and transmittance spectra, the contents of Co, Co²⁺ ions and phases in the films were quantitatively determined. The pressure dependence of Co contents in the films was given. The correlations between room-temperature magnetism and the Co, Co²⁺ ions and phases in the films are discussed quantitatively. It is found that the Co content in the film decreases with the increase of oxygen pressure during the deposition. Most of Co atoms are determined to be Co²⁺ ions entered the ZnO lattice to substitute for Zn²⁺ ions, but not being responsible for the magnetism of the films at room temperature. The metallic Co nano-clusters are detected by fine XRD analysis in the films deposited at 0.0001 Pa and 5.0 Pa, being consistent with the estimation using the room-temperature magnetism of the films. On the basis of quantitative analysis, a superparamagnetic magnetization mechanism of metallic Co nano-clusters is suggested and is compared with experimental results by quantitative calculation.

Key words: Co-doped ZnO, diluted magnetic semiconductors, magnetic property, magnetization mechanism, quantitative analysis

CLC Number:

O482

LIU Xue-Zhen, BAO Shan-Yong, ZHANG Huan-Huan, MA Chun-Yu, XU Xiao-Ming, ZHANG Qing-Yu . Study on the Magnetism of Epitaxial ZnCoO Films Deposited by Pulsed Laser Deposition[J]. Journal of Inorganic Materials, 2012, 27(4): 369-374.

Figures/Tables 6

Fig. 1 (a) XRD patterns of Zn1-xCoxO films deposited at different oxygen pressures; inset is the rocking curves of (002) diffraction peaks; (b) Epitaxial relationship between Zn1-xCoxO film and sapphire substrate

Fig. 2 (a) Magnetization curves of Zn1-xCoxO films, the inset is original magnetization curves of ZnO buffer and ZnCoO film deposited at 0.0001 Pa, (b) M-T curve of Co-doped ZnO film deposited at 0.0001 Pa, H=39800 A/m; the inset is magnetization curve of the film at 10 K

Fig. 3 Transmission spectra of Zn1-xCoxO films deposited at different oxygen pressures

Fig. 4 (a) Absorption coefficients of Zn1-xCoxO films deposited at different oxygen pressures, (b) Absorption coefficients for Co2+ ions in the Zn1-xCoxO films

Fig. 5 Fine XRD patterns of Zn1-xCoxO films deposited at different oxygen pressures

Fig. 6 Calculated RT magnetization curve

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