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| MICROSTRUCTURE, MAGNETIC AND MAGNETOTRANSPORT PROPERTIES OF Co-C NANOCOMPOSITE THIN FILMS |
| TANG Ruihe1), YANG Zhigang1), ZHANG Chi1), YANG Bai2), LIU Xiaofang2), YU Ronghai2) |
1) Key Laboratory of Advanced Materials, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084
2) School of Materials Science and Engineering, Beihang University, Beijing 100191 |
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Cite this article:
TANG Ruihe YANG Zhigang ZHANG Chi YANG Bai LIU Xiaofang YU Ronghai. MICROSTRUCTURE, MAGNETIC AND MAGNETOTRANSPORT PROPERTIES OF Co-C NANOCOMPOSITE THIN FILMS. Acta Metall Sin, 2011, 47(4): 469-474.
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Abstract Co-C nanocomposite thin films with a Co atomic content of 13.0% were fabricated onto Si (100) substrates by magnetron co-sputtering technique. Post annealing was carried out in vacuum at annealing temperature ranging from 473 K to 773 K for 30 min. TEM images indicate that the Co nanoparticles are dispersed uniformly in an amorphous carbon matrix for the as-deposited samples, and Co particle size is in a range of 1.5-3.0 nm. After annealing at 673 K, the average Co particle size is enlarged distinctly. Magnetization hysteresis loops reveal that the as-deposited thin films show low magnetization. As annealing temperature is increased, both magnetization and coercivity are enhanced significantly. The samples annealed at 673 K and 773 K show ferromagnetic behaviors at low temperature, and superparamagnetic behaviors at room temperature, which are characteristic magnetic features for granular system. A negative magnetoresistance (MR) of 1.33% is observed for the as-deposited Co-C thin films at 4.2 K in the applied magnetic field of 3980 kA/m. The MR value decreases with increasing annealing temperature. Resistance (R) versus temperature (T) curves exhibit a good linear relationship of lnR-T-1/4 at a broad low temperature range, suggesting that the conduction in Co-C nanocomposite thin films follows the variable range hopping transport mechanism.
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Received: 13 October 2010
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| Fund: Supported by National Natural Science Foundation of China (Nos.50771058 and 50729101) and the National Major Fundamental Research Program of China (No.2010CB934602) |
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