Magnetization and stability study of a cobalt-ferrite-based ferrofluid

In this study the structural and magnetization properties of a CoFe₂O₄-based ferrofluid was investigated using x-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDS), Mössbauer spectroscopy, and magnetic Compton scattering (MCS) measurements. The XRD diagram indicates that the nanoparticles in the ferrofluid are inverse spinel and TEM graph shows that the ferrofluid consists of spherical nanoparticles with an average diameter of 18± 1 nm, in good agreement with the size, 19.4 nm, extracted from line broadening of the XRD peaks. According to EDS measurements the composition of the nanoparticles is CoFe₂O₄. Mössbauer spectroscopy shows that the cation distributions are (Co_0.38Fe_0.62)[Co_0.62Fe_1.38]O₄. The MCS measurement, performed at 10 K, indicates that the magnetization of the nanoparticles is similar to magnetization of maghemite and magnetite. While the magnetization of the inverse spinels are in [111] direction, interestingly, the magnetization deduced from MCS is in [100] direction. The CoFe₂O₄-based ferrofluid is found to be stable at ambient conditions, which is important for applications.