Room-temperature ferromagnetism on ZnO nanoparticles doped with Cr: An experimental and theoretical analysis

The experimental and theoretical structural, optical, and magnetic properties of Cr modified Zinc Oxide nanoparticles synthesized by thermal decomposition route were studied, finding a good agreement between them. Rietveld refinement of the XRD data shows that the samples belong to the P63mc space group with a Wurtzite structure. Moreover, a slight decrease in lattice parameters indicates that Cr substitutes Zn atoms in the lattice. The absorption spectra show a decrease in bandgap energy with increasing Cr doping, confirming the decisive role of Cr ion in the optical properties of ZnO. First-principles calculations also confirmed the reduction of the band-gap because of the introduction of impurity states. Magnetic measurements exhibit room temperature weak-ferromagnetism (RTFM) and increase the remnant magnetization (M-r) with increasing Cr doping. Furthermore, first-principles calculations demonstrate the presence of ferromagnetism for Cr doping up to 8% supported by experimental results. When Cr doping is 8%, theoretical results suggest possible agglomeration of the Cr atoms to form metallic-antiferromagnetic chromium oxide. However, when Cr is well dispersed into the lattice -as suggested by XRD measurements-, both ferromagnetic and antiferromagnetic behavior are degenerated, making possible the room-temperature ferromagnetic behavior. (C) 2020 Elsevier B.V. All rights reserved.