Magnetic properties of microwave-synthesized Mn-doped SnO2 nanoparticles

Abstract

Semiconductor nanostructures with dilute magnetic property are of great importance for different applications. However, this property depends on several factors including the synthesis route. In this work, manganese (Mn)-doped tin dioxide (SnO2) nanoparticles (NPs) at different concentrations were synthesized by the microwave-assisted synthesis method and evaluated for their magnetic properties. The X-ray diffraction analyses revealed a single-phase rutile-type tetragonal structure, while SEM and TEM images showed fine NPs with average sizes around 10 nm. A considerable increase in value of the energy band gap by around 0.18 eV as a result of Mn doping was observed. This dopant has also increased the lattice d-spacing value, but slightly decreased the lattice constant c. The magnetic measurement result showed that all the microwave-synthesized Mn-doped SnO2 NPs including the pure one have distinctly wide hysteresis loops, indicating that samples have room temperature ferromagnetism (RTFM). RTFM was further enhanced by Mn doping reaching maximum at a concentration of 0.3 mol%. This magnetism could be attributed to the presence of defects at the grain boundaries within the NPs, interfacing sites between the NPs, oxygen or tin vacancies and an optimum level of Mn dopant. The observed wide hysteresis loops in these samples might be due to the use of a surfactant at high concentration that could provide highly compact/tight NPs. These results might be useful for producing nanoscale magnets and magnetic memory devices.