Physical investigations on NiMn2O4 sprayed magnetic spinel for sensitivity applications

Abstract

NiMn2O4 ternary nickel manganese oxide thin films spinels have been grown on glass substrates at 350°C through spray pyrolysis technique. X-ray diffraction and Raman spectroscopy analyses show that the synthesized film has mainly cubic spinel structure with a preferred orientation along (111) plane. Some optical constants such as the refractive index (n), extinction coefficient (k), Urbach energy (EU=342eV) and optical energy band gap (Eg=1.07eV) have been calculated from reflection-transmission spectra. The mirage effect technique has been used to estimate the thermal conductivity (Kc). Its value is Kc=25Wm−1K−1. The real part of the ac the conductivity behaviour has been investigated in the frequency range 100Hz to 1MHz. It was found that the real conductivity follows a power law (Aωs). The dc conductivity has been studied in the temperature range from 250°C to 375°C and supports the variable range hopping model proposed by Mott. The activation energy value estimated from the relaxation frequency is Ea~0.32eV. Moreover, the temperature dependency of the resistance indicates that conduction was well described by a variable range hopping model, in which electron transfer takes place between Mn3+ and Mn4+ ions.