Physical investigations on NiMn sub(2)O sub(4) sprayed magnetic spinel for sensitivity applications

NiMn sub(2)O sub(4) ternary nickel manganese oxide thin films spinels have been grown on glass substrates at 350[degrees]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 (E sub(U)=342 eV) and optical energy band gap (E sub(g)=1.07 eV) have been calculated from reflection-transmission spectra. The mirage effect technique has been used to estimate the thermal conductivity (K sub(c)). Its value is K sub(c)=25 W m super(-1) K super(-1). The real part of the ac the conductivity behaviour has been investigated in the frequency range 100 Hz to 1 MHz. It was found that the real conductivity follows a power law (Aoo super(s)). The dc conductivity has been studied in the temperature range from 250[degrees]C to 375[degrees]C and supports the variable range hopping model proposed by Mott. The activation energy value estimated from the relaxation frequency is Ea~0.32 eV. 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 Mn super(3+) and Mn super(4+) ions.