Microstructural, magnetic, and optical properties of Zn1−x(Mnx∕2Cox∕2)O (x=0.1 and 0.2) semiconducting nanoparticles

We have investigated structural, magnetic, and optical properties of ${\mathrm{Zn}}_{1-x}\left({\mathrm{Mn}}_{x∕2}{\mathrm{Co}}_{x∕2}\right)\mathrm{O}$ ($x=0.1$ and 0.2) diluted magnetic semiconducting nanoparticles synthesized by chemical “pyrophoric reaction process.” X-ray diffraction analysis clearly shows that the samples are single phase in ZnO wurtzite structure, where the average crystallite size of samples is found to be in the nanometric regime $(\sim 10\mathrm{nm})$ . From the Curie-Weiss fit, as well as from the calculated value of effective exchange constant $\left(J_{\mathrm{ex}}\right)$ , which is found to be negative, we can assert that the nature of magnetic ground state of both of these samples are antiferromagnetic (AFM). This is further established by the concave nature of isothermal Arrott-Belov-Kouvel plots at the ground state $\left(5\mathrm{K}\right)$ without having any spontaneous magnetization in both of the samples. When both Mn and Co dopant concentrations $\left(x\right)$ are increased in the ZnO matrix, the magnitude of AFM interaction $\left(\mid J_{\mathrm{ex}}\mid \right)$ is found to enhance. This observed magnetic behavior has been best explained through the bound magnetic polaron-polaron interaction model. The semiconducting band gap of those nanoparticles has been estimated using recorded optical absorbance spectra.