Iron(II)-induced defect luminescence and deconvolution of ferromagnetic and paramagnetic behaviour in Zn(1-x)FexO (x = 0.01, 0.03, 0.05) nanoparticles

Abstract

Zn(1-x)FexO (x = 0.00, 0.01, 0.03, 0.05) nanoparticles (NPs) were prepared by co-precipitation method and the wurtzite phase was confirmed by x-ray diffraction (XRD). The average crystallite size changes from 36 nm to 26 → 23→22 nm as the Fe-doping level varies from 0 to 1% → 3% → 5 % and the lattice strain increases concomitantly. The pristine ZnO NPs exhibit well-defined peak at 370 nm in the UV–vis absorption spectra which gets broadened on Fe-doping. The photoluminescence (PL) spectra of the pristine ZnO NPs shows a dominant excitonic peak at 390 nm. On Fe(II)-doping, new PL peaks at 449, 490 and 525 nm appear that are attributed to Zn-interstitials (Zni), oxygen vacancies (VO) and Zn vacancies (VZn), respectively. For all the Fe-doped ZnO NPs, M vs H plots have a complex non-saturating appearance indicating combination of ferromagnetic (FM) and paramagnetic (PM) behaviors. The subtraction of PM contribution revealed the FM curves with saturation magnetization (Ms). On going from 1% to 5% Fe-doping, the Ms values increase substantially by 39 times (0.00361 → 0.1398 emu/g) whereas the paramagnetic susceptibility, χP, increased 35 times (0.28 × 10−6 → 9.72 × 10−6 emu g−1 Oe−1).