Lai Fa-chun

Effects of Samarium Doping on Optical Properties of Zn0.9(Co1-xSmx)0.1O Diluted Magnetic Semiconductor

Abstract Transparent ZnO and Zn 0.9 (Co 1-x Sm x ) 0.1 O ( x = 0.0, 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.0) films were prepared by sol-gel method. For the prepared Zn 0.9 (Co 1-x Sm x ) 0.1 O systems, the influences of dopant concentration of Sm on the structural and optical properties were investigated. Three additional absorption peaks around 570, 620, and 660 nm wavelengths were observed in low Sm content films, which is attributed to the d-d transitions of Co 2+ ions in tetrahedral crystalline. The redshift of band gap in doped samples was discussed in detail.

Enhanced Magnetoresistance of (La0.67Ca0.33MnO3) Composites Coated by Zn0.95Co0.05O

La0.7Ca0.3MnO3:xZn0.95Co0.05O (x = 0.0, 0.05, 0.1, 0.15 mol) composites are prepared by a sol-gel process. X-ray diffraction and energy diffraction spectroscopy reveal that there is no evidence of a reaction between the La0.7Ca0.3MnO3 (LCMO) and Zn0.95 Co0.05 O (ZCO). Magnetization M, Curie temperature TC and metal-insulator transition temperatures Tp are observed to decrease with increasing ZCO content. Compared with x = 0.0, a great enhancement in the magnetoresistance (MR) is observed at around TC for x = 0.05, 0.10, 0.15. Based on the tunneling MR and percolation models, this great change of MR is well explained.