Low field room temperature magnetism and band gap modifications in Sm doped SnO₂

The structural, optical and magnetic properties of pure and Sm doped SnO₂ nanoparticles synthesized in aqueous solution by a low cost chemical co-precipitation method without using any stabilizing agent have been reported. X-ray diffraction analysis reveals that the crystallite size of SnO₂ decreases with the increase of Sm doping into the SnO₂ matrix. The calculated value of optical band gap of undoped SnO₂ nanoparticles is calculated to be 2.65 eV and it anomalously increases with the increase of Sm³⁺ concentration. The band gap of undoped SnO₂ nanoparticles is found to be lower than those reported for bulk SnO₂ (3.6 eV) that may be due to the presence of defects, oxygen vacancies and non-stoichiometry of SnO₂ nanoparticles. All the undoped and Sm doped SnO₂ nanoparticles show weak room temperature magnetism in the range of applied low magnetic field region of 2000 Oe due to the presence of defects and oxygen vacancies. All the samples exhibit negative magnetic susceptibility for the applied magnetic field higher than 2000 Oe. The strong optical absorption with weak magnetic properties at room temperature may serve the SnO₂ nanomaterials as a potential candidate for many DMS, spintronics, and optoelectronics based applications.