Raman spectroscopy and dielectric Studies of multiple phase transitions in ZnO:Ni

Abstract

We present Raman and dielectric data on Ni-doped ZnO $\left({\mathrm{Zn}}_{1-x}{\mathrm{Ni}}_x\mathrm{O}\right)$ ceramics as a function of Ni concentration ($x=0.03$ , 0.06, and 0.10) and temperature. A mode (around $130{\mathrm{cm}}^{-1}$ ) is identified as $\mathrm{TA}\left(M\right)$ [J. M. Calleja and M. Cardona, Phys. Rev. B 16, 3753 (1977)] and appears due to an antiferromagnetic phase transition at low temperatures $\left(100\mathrm{K}\right)$ via the spin-orbit mechanism [P. Moch and C. Dugautier, Phys. Lett. A 43, 169 (1973)]. A strong dielectric anomaly occurs at around $430–460\mathrm{K}$ , depending on Ni concentration, and is due to extrinsic electret effects (Ni ionic conduction) and not to a ferroelectric phase transition.