  In this paper, we establish the existence of both compressive stress and
charge transfer process in hydrothermally synthesized cobalt ferrite-graphene
oxide (CoFe2O4/GO) nanocomposites. Transmission electron microscopy (TEM)
results reveal the decoration of CoFe2O4 nanoparticles on GO sheets. Magnetic
response of nanocomposites was confirme from superconducting quantum
interference device (SQUID) magnetometer measurement. Optical properties of
these nanocomposites were investigated by Raman spectroscopy. Interfacial
compressive stress involved in this system is evaluated from observed blue
shift of characteristic G peak of graphene oxide. Increase in full width
half-maximum ( FWHM) as well as up shift in D and G peaks are clear indicator
of involvement of charge transfer process between GO sheets and dispersed
magnetic nanoparticles. The effect of charge transfer process is quantified in
terms of shifting of Fermi level of these nanocomposites. This is evaluated
from variation in contact surface potential difference (CPD) using Scanning
Kelvin probe microscopy (SKPM). XRD spectra of CoFe2O4/GO confirm the
polycrystalline nature of CoFe2O4 nanoparticles. Lattice strain estimated from
XRD peaks are correlated to the observed Raman shift.
