Genesis and tuning of ferromagnetism in SnO2 semiconductor nanostructures: Comprehensive review on size, morphology, magnetic properties and DFT investigations

Wide bandgap oxide semiconductors with controllable sizes are an interesting class of nanomaterials due to their applications in spintronic and magneto-optical devices. In recent times, tin dioxide (SnO2) an important class of n-type wide-band gap semiconductor in the nanoscale regime, has drawn considerable research interest owing to high optical transparency, high chemical/thermal stability and controllable optical and magnetic properties. Although bulk SnO2 is diamagnetic due to lack of unpaired electrons, SnO2 nanostructures with different morphology rope the formation of inherent defects and contribute defects induced ferromagnetism. Besides morphology-dependent magnetic properties, transition metal doping into the nanoscale SnO2 crystal lattice endows tuneable magnetic properties. Here, we outline the synthesis strategies of SnO2 based nanostructures with different morphology, including quantum dot, nanowire, nanotube, nanosheet, 3D-hierarchal flower-like structure and thin film. In addition to the pristine SnO2 nanostructures, size, morphological and doping repercussions on the magnetic properties of single and double transition metal (TM)-doped SnO2 nanostructures are also reviewed. Density functional theory (DFT) investigation of pristine and TM-doped SnO2 systems is reviewed and the correlations between certain experimental results are explored. Finally, an outlook and challenges in understanding the basis of origin and control of ferromagnetism in SnO2-based nanostructures are conferred.