Effect of reaction temperature on electrical and magnetic properties of chemically synthesized MnS nanocrystals

Abstract

In the present work, MnS nanocrystals have been synthesized using a wet chemical technique with three different precursor reaction temperatures in the range of 55 °C–75 °C. The high precision LCR measuring instrument was used to study the dielectric and electrical properties of the MnS nanocrystals in terms of complex dielectric constant, complex impedance, complex electric modulus, and AC electrical conductivity. The effects of grains and grain boundaries on the dielectric relaxation and the electrical conduction mechanism of the material have been investigated with the frequency (50 Hz–5 MHz) of the applied field at different temperatures (323 K–473 K). The dielectric measurements have confirmed the presence of dipolar and interfacial polarization in the structure. The dielectric constant and loss tangent were found to decrease with the increasing reaction temperature. The complex impedance and the electric modulus investigation revealed the presence of a non-Debye type of relaxation in the samples. The Cole-Cole plot and the conductivity studies have confirmed a typical NTCR behavior in the as-synthesized MnS nanocrystals. The activation energy calculated from the Arrhenius equation was found to be 0.27 eV, 0.34 eV, and 0.38 eV for the samples synthesized at 55 °C, 65 °C and 75 °C respectively. VSM measurements revealed that the saturation magnetization increase and coercivity decrease with the increasing reaction temperature. Furthermore, the effective magnetic anisotropy constant, the particle volume, and the relaxation time of the MnS nanocrystals were estimated. The magnetic measurements confirmed that all the samples exhibit paramagnetic behavior.