Magneto-optical effect of (Sm, Co) co-doping in ZnO semiconductor

Abstract

In this paper, the effect of (Sm, Co) co-doping on the structure, optical and magnetic properties of ZnO nanoparticles was studied. Pure ZnO and (Sm, Co) co-doped nanoparticles, Zn1-2xSmxCoxO with x = 0.00, 0.005, 0.01, 0.02, 0.04 and 0.06, were synthesized by co-precipitation technique. The X-rays diffraction (XRD) scans were performed with 2θ varies from 20° to 80°.The XRD patterns of all samples confirmed the formation of wurtzite-type structure of ZnO with the formation of Sm2O3 and Co3O4 as minor secondary phases with x ≥ 0.005. The spherical morphology of pure ZnO is transformed to nanorods as the concentration of Sm3+ and Co2+ increases. The diameter and length of the nanorods were nearly 35.1–66.5 nm and 136.2–596 nm, respectively. UV–vis spectra were used for the calculation of the energy band gap (Eg) by different methods. Eg is found to increase with increasing (Sm, Co) doping up to x = 0.02. Energy band gap and Urbach energy are observed to have a reverse trend. Magnetic properties were investigated by the vibrating sample magnetometer. M − H hysteresis analysis reveals that for small doping, the samples have a ferromagnetic signal combined with diamagnetic contribution. The enhancement in ferromagnetism behaviour for 0.01 < x < 0.02 was justified by the formation of Bound Magnetic Polarons (BMPs) as it significantly enhances with the doping of Sm and Co by stabilizing Zn vacancy and other magnetic defects. Then the ferromagnetism is reduced for the doped samples up to x = 0.06, and an antiferromagnetic alignment is displayed.