Synthesis of single phase FexSn1−xO2 nanoparticles with enhanced structural, optical and magnetic properties

Abstract

Single phase FexSn1−xO2 nanoparticles of size 2–16 nm were synthesized by simple co-precipitation method. The X-ray diffraction (XRD) pattern shows pure tetragonal rutile phase of SnO2 without any indication of other impurity phases related to Fe doping. A systematic decrease in the crystallinity (increased peak broadening) was observed with increasing doping percentage owing to the increase in distortion and tensile nature of residual compressive strain. The optical band gap energy of the FexSn1−xO2 nanoparticles decreases from 3.68 eV to 2.35 eV with increasing Fe content. The observed tunable optical properties with Fe-doping variations can be attributed to the replacement of Sn4+ ions by Fe3+/2+ ions in tetragonal rutile phase of SnO2 with no evidence of metallic Fe. The room temperature photoluminescence spectra of FexSn1−xO2 nanoparticles show broad emissions at about 347 and 437 nm under 270 nm excitations. These emissions correspond to the introduction of Fe-impurity, defect concentration and the possibility that both the hole and the electron can trap in the oxygen vacancy sites at the surface of the SnO2 nanoparticles which act as recombination center generating the non-radiative emissions. Vibrating sample magnetometer (VSM) measurement suggests that the pure SnO2 possess diamagnetic behavior while doped nanoparticles exhibit ferromagnetic to superparamagnetic transitions. Initially, these nanoparticles showed strong ferromagnetic behavior at room temperature, however at higher doping percentage of Fe, the ferromagnetic behavior was covered up, and antiferromagnetic nature was dominated. The enhanced antiferromagnetic interaction between adjacent Fe-Fe ions covered up the ferromagnetism at higher doping concentrations of Fe. The value of magnetic moment of the sample increases with Fe concentration and attains maximum value of 0.121178 μB. The co-existing magneto-optical properties make the FexSn1−xO2 nanoparticles a promising candidate for various magneto-electronic and spintronics related applications, underlying the findings and importance of current investigations.