• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.148-149
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• 2002

In recent years, semiconductor spintronics has been rapidly developing due to potential device applications, in which the spin of charge carriers (electrons or holes) provides novel functionalities to carry signals and process information. Diluted magnetic semiconductors (DMSs) are well known to exhibit intriguing properties such as carrier-mediated ferromagnetism and spin-dependent transport resulting from the coupling between the charge transport states and the magnetic moments (spin) [1-3]. (omitted)

• Journal of the Korean Ceramic Society
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• v.43 no.2 s.285
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• pp.79-84
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• 2006

We studied the microstructure and magnetic property of the pulsed DC magnetron sputtered $Zn_{\0.8}Co_{0.2}O$ film as a function of substrate temperatures. The X-ray patterns of the $Zn_{\0.8}Co_{0.2}O$ film showed a strong (002) preferential orientation at $500^{\circ}C$. The films with a crystallite size of 23-35 nm were grown in the form of nano-sized structure and this tendency was remarkable with increasing substrate temperature. The UV-visible result showed that the $Zn_{\0.8}Co_{0.2}O$ film prepared above $300^{\circ}C$ has a high optical transmittance of over $80\%$ in the visible region. The absorption bands were observed due to sp-d interchange action by $Co^{2+}$ complex ion and dd transition in the region from 500 to 700nm. The resistivity of the film was below $10^{-1}\;\Omega-cm\;above\;300^{\circ}C$. The AGM analysis results for the all films showed the magnetic hysteresis curves of ferromagnetic nature. The low electrical resistivity and room temperature ferromagnetism of ZnCoO thin films 'deposited above $300^{\circ}C$ suggested the possibility for the application to Diluted Magnetic Semiconductors (DMSs).

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.94-95
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• 2002

Recently, we have seen a rapid advance in the evolving field of spin electronics (or spintronics). In spintronics, some feasibilities of new electronic applications utilizing spin degree of freedom have been explored. Diluted magnetic semiconductors (DMSs) are premising materials for spintronics because they have both charge and spin degree of freedom in a single substance. DMSs are refereed to semiconductor alloys in which some atoms are randomly substituted for by magnetic atoms. (omitted)

• Proceedings of the Korean Magnestics Society Conference
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• 2003.06a
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• pp.266-267
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• 2003

The most distinguishing character of diluted magnetic semiconductors (DMSs) is a strong interaction between sp-carriers and localized d-spins (sp-d exchange interaction). Recently many "room-temperature (RT) ferromagnetic DMS" have been reported. However, it should be noted that their sp-d exchange interactions have not been confirmed yet. The lack of a clear evidence of the sp-d exchange interaction causes the controversy on the origin of the observed ferromagnetism. For the detection of the sp-d exchange interaction, magneto-optical spectroscopy such as a magnetic circular dichroism (MCD) measurement is the most powerful tool. By using the MCD spectroscopy, we have shown the sp-d exchange interactions in Zn$_{l-x}$Cr$_{x}$Te. Recently, we have obtained the RT ferromagnetism in a Zn$_{l-x}$Cr$_{x}$Te (x = 0.20) film.0) film.

• Journal of the Korean Chemical Society
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• v.54 no.6
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• pp.766-770
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• 2010

This is the study of magnetic properties of transition metal doped diluted magnetic semiconductors(DMSs). The wurtzite structure samples were synthesized by the sol-gel method. The thermodynamic characteristics and magnetic properties of $Zn_{1-x}Co_xO$ single phase was investigated for different doping concentration (x = 0%, 1%, 2%, 3%, 4%, 5%, 10%, 15%). The property of diluted magnetic semiconductors has been comfirmed by X-ray diffraction (XRD), Scanning Electronic Microscope (SEM) and Vibrating sample magnetometer (VSM). The magnetic properties of pure $Zn_{1-x}Co_xO$ is found to be dominated by the ferromagnetic interaction between doped transition metal ions, where by the ferromagnetic coupling strength is simply increased with the concentration(>5%) of the doped transition metal.

• Journal of the Korean Ceramic Society
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• v.42 no.3 s.274
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• pp.211-217
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• 2005

[ $Zn_{1-x}Co_{x}O$ (x=0-0.3) films were grown on Corning 7059 glasses by asymmetrical bipolar pulsed dc magnetron sputtering. The c-axis orientation along (002) plane was enhanced with increasing Co concentration. The $Zn_{1-x}Co_{x}O$ films are grown with fibrous grains of tight dome shape. The transmittance spectra measured from UV-visible showed that sp-d exchange interactions and typical d-d transitions become activated with increasing Co concentration. The electrical resistivity of $Zn_{1-x}Co_{x}O$ films increased with increasing Co concentration, especially it increased greatly at $30at\% Co. X-ray photoelectron spectroscopy and alternating gradient magnetometer analyses indicated that no Co metal cluster is formed and the ferromagnetic properties are exhibited. The low electrical resistivity and room temperature ferromagnetism of $Zn_{1-x}Co_{x}O$ thin films suggested the possibility of the application to Diluted Magnetic Semiconductors (DMSs).