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

Abstract

In this work, Fe 3 O 4 nanoparticles and amorphous silica coated Fe 3 O 4 @SiO 2 nanocomposites synthesized using solvothermal method and modified Stöber method are reported. Powder XRD analysis, FTIR spectroscopic technique and X-ray photoelectron spectroscopy analyzeswere employed to confirm the structure and formation of Fe 3 O 4 nanoparticles and Fe 3 O 4 @SiO 2 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 Fe 3 O 4 @SiO 2 core shell structured nanocomposites. VSM analysis confirms super paramagnetic features having soft magnetic property in Fe 3 O 4 @SiO 2 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 Fe 3 O 4 @SiO 2 displays positive temperature coefficient of resistance type behavior and the frequency dependent ac conductivity obeys the well-known Jonscher’s power law. • Fe 3 O 4 @SiO 2 core shell nanocomposites are prepared using modified Stober process. • The value of magnetic saturation is high for Fe 3 O 4 and low for Fe 3 O 4 @SiO 2 core shell structured nanocomposites. • FTIR, XPS and TEM measurements substantiate the formation of Fe 3 O 4 @SiO 2 core shell structured nanocomposites. • When the temperature is high the dielectric constant is high and the dielectric loss is low at lower frequency region. • The cole-cole plot reveals that the material follows non-Debye type of relaxation.