Enhanced Ferromagnetism in Nano-sized Sn_0.85Co_0.10Fe_0.03Mn_0.02O₂ Dilute Magnetic Semiconductor Synthesised by Sol–Gel Method

Co-Fe–Mn co-doped SnO₂ nanoparticles have been effectively synthesised by sol–gel method. To explore the effect of co-doping in instigating room-temperature ferromagnetism in SnO₂ nanocrystals, the structural, optical and magnetic behaviours of Sn_0.85Co_0.10Fe_0.03Mn_0.02O₂ nanoparticles were examined. Also, the oxidation states of dopants were evaluated using XPS analysis. XRD data exhibited pure SnO₂ phase, revealing the effectiveness of the method of synthesis in substituting the dopant ions into Sn sites. The average crystallite size of the synthesised sample was calculated to be 21 nm. SEM–EDX and HRTEM-SAED revealed the surface morphology, elemental composition, lattice plane and the polycrystalline nature of the nanoparticles. Diffuse reflectance spectroscopy data illustrated a decrease in bandgap compared to bulk SnO₂ due to the effect of dopants. FTIR spectrum disclosed the prominent peaks corresponding to SnO₂. The occurrence of room-temperature ferromagnetism in the prescribed sample has been validated from the magnetic hysteresis plotted using VSM data analysis. The analysis of all the abovementioned characterisations revealed the incorporation of dopants into SnO₂ host material. The emergence of magnetism in the sample depends mainly on the distribution of vacancy defects and nano-size of the sample, in addition to the surface diffusion of magnetic dopant ions into the SnO₂ lattice.