Annealing-induced enhancement of ferromagnetism in SnO2-core/Cu-shell coaxial nanowires |
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Authors: | Hyoun Woo Kim Han Gil Na Ju Chan Yang Jinho Ahn Chong Seung Yoon Heon Ham Kwang Bo Shim Changhwan Choi Inpil Kang Jae-Hak Yang Chongmu Lee |
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Affiliation: | 1. Division of Materials Science and Engineering, Hanyang University, Seoul, 133-791, Korea 2. School of Materials Science and Engineering, Inha University, Incheon, 402-751, Korea 3. Department of Mechanical and Automotive Engineering, Pukyong National University, Busan, 608-739, Korea 4. Advanced Materials R&D Center, Korea Institute of Industrial Technology, Incheon, 406-840, Korea
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Abstract: | In this study, we have coated tin oxide (SnO2) nanowires with a Cu shell layer via the sputtering method and subsequently investigated the effects of thermal annealing. The annealing-induced changes in morphologies, microstructures, and compositions of the resulting core-shell nanowires were characterized by using scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and energydispersive X-ray spectroscopy (EDX). The Cu shell layers were agglomerated to form clusters, which were mainly comprised of the Cu2O phase. For the first time, a hysteresis loop indicating weak ferromagnetism was observed from the pure SnO2 nanowires. Both the coercivity and the retentivity in the hysteresis loop were slightly increased by Cu-sputtering, indicating a very slight enhancement of ferromagnetism. Also, the ferromagnetic behavior was significantly enhanced by thermal annealing. We discuss the possible mechanisms of annealing-induced enhancement of ferromagnetism in the SiO2/Cu core-shell nanowires, which include the generation of Cu2O phase, Cu-doping into the SnO2 lattice, and the generation of oxygen vacancies in SnO2 core nanowires. |
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