Structural characterization and properties of nanocrystalline Sn1-xCoxO2 based dilute magnetic semiconductors

Monophasic Sn1-xCoxO2 (x = 0.05, 0.10, and 0.15) nanoparticles with tetragonal structure have been successfully synthesized by solvothermal method using oxalate precursor route. Powder x-ray diffraction and selected area electron diffraction studies confirmed highly crystalline cassiterite SnO2 structure. The contraction of lattice constants confirmed the incorporation of Co2+ in SnO2 host lattice. Hexagonal nanoparticles with average grain size of 8-13 nm have been formed. With the increasing Co content, the decreasing crystallite size of SnO2 with increasing surface areas from 194 to 219 m(2)/g was found. The percentage reflectance increases on increasing the cobalt concentration, and a noticeable blue shift appeared. The band gap was found to be 3.85, 3.91, and 4.09 eV, respectively. Co-doped SnO2 showed distinct magnetic behavior with different Co2+ concentration. For x = 0.05 and 0.10, nanoparticles showed paramagnetism with antiferromagnetic interaction, however, on further increasing x = 0.15, the nanoparticles showed canted antiferromagnetic coupling.