Impact of amorphous SiO2 as shell material on superparamagnetic Fe3O4 nanoparticles and investigation of temperature and frequency dependent dielectric properties

In this work, Fe3O4 nanoparticles and amorphous silica coated Fe3O4@SiO2 nanocomposites synthesized using solvothermal method and modified Stober method are reported. Powder XRD analysis, FTIR spectroscopic technique and X-ray photoelectron spectroscopy analyzeswere employed to confirm the structure and formation of Fe3O4 nanoparticles and Fe3O4 @SiO2 core shell structured nanocomposites. The structural details elucidated from TEM images and SAED patterns are very much in agreement with the XRD results and confirm the formation of Fe3O4@SiO2 core shell structured nanocomposites. VSM analysis confirms super paramagnetic features having soft magnetic property in Fe3O4@SiO2 albeit with reduction in saturation magnetization. The dielectric behavior was studied at different temperatures in the frequency range between 1 Hz and 1 MHz in the temperature range 373 K to 723 K in steps of 50 K. The modulus spectrum formalism reveals temperature dependent hopping type of mechanism for charge transport and the impedance spectra reveals the contribution of grain effect on the electrical properties. Further, the analysis of dielectric data indicates that the Fe3O4@SiO2 displays positive temperature coefficient of resistance type behavior and the frequency dependent ac conductivity obeys the well-known Jonscher's power law. (C) 2022 Published by Elsevier B.V.

Automated summary

This study reports the synthesis of Fe3O4 nanoparticles and Fe3O4@SiO2 nanocomposites coated with amorphous silica using solvothermal and modified Stober methods. Various analysis techniques were employed to confirm their structure and formation, and their magnetic and electrical properties were investigated.