Exploration of Raman spectroscopy, dielectric and magnetic properties of (Mn, Co) co-doped SnO2 nanoparticles

Abstract

The comprehensive investigation of Raman modes, magnetic and dielectric properties have been carried out on Mn-Co co-doped SnO2 nanoparticles by fixing Mn content (5%) and varying doping concentration of Co (0%, 1%, 3%, and 5%). Average crystallite size estimated from Williamson Hall analysis is found to be in decreasing order on increasing concentration of Co and ranging between 29.4 nm and 19.2 nm. Transmission electron microscopy analysis gives evidence that the pre-synthesized Mn-Co co-doped SnO2 powder samples contain nanoparticles with particle size 24.5 nm for 5% Mn doped SnO2 and 14.5 nm for 5% Mn + 5% Co co-doped SnO2. These nanoparticles exhibit a very strange ferromagnetic to superparamagnetic transition and superparamagnetic phase of the samples grows on increasing Co content. This improved superparamagnetic phase in Mn-Co co-doped SnO2 nanoparticles may offer ferrofluids and several biomedical applications like MRI, drugs delivery, hyperthermia, etc. The origin of electric polarization in the Mn-Co co-doped SnO2 nanoparticles has been explained on the basis of dielectric permittivity and typical dielectric dispersion. The small polaron hopping and correlated barrier hopping was found as a dominating ac conduction mechanism in 5% Mn doped SnO2 and heavily co-doped (5% Mn + 5% Co) SnO2. The typical behavior of increasing ac activation energy in Mn-Co co-doped SnO2 samples with frequencies have also been depicted.