Structural and magnetic studies of Mn-doped ZnO

The bulk samples of Mn-doped ZnO were synthesized with the nominal compositions Zn1-xMnxO (x= 0.02, 0.05, 0.10, 0.15) by the solid-state reaction and sol-gel methods. In both the methods the samples were finally sintered at similar to 700 degrees C in air. The X-ray diffraction (XRD) studies of the samples synthesized by the solid-state reaction method exhibit the presence of wurtzite (hexagonal) crystal structure similar to the parent compound (ZnO) in all the samples, suggesting that doped Mn ions sit at the regular Zn sites. However, same studies spread over the samples with Mn content >= 5% and synthesized by the sol-gel method reveal the occurrence of some secondary phase in addition to the majority wurtzite phase. The magnetic measurements by vibrating sample magnetometer (VSM) clearly indicate ferromagnetic interaction at room temperature in all the samples. The Curie temperatures (Tc) and magnetization vary with concentration of Mn ions in the samples. However, the samples synthesized by sol-gel method were found to have lower Tc values and also lower magnetization as compared to the corresponding samples synthesized by solid-state reaction method. It could possibly be due to the presence of antiferromagnetic islands and smaller crystallite sizes in the samples prepared by sot-gel method. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.