Bimagnetic hard/soft and soft/hard ferrite nanocomposites: Structural, magnetic and hyperthermia properties

Recent studies show that the chemical composition and shape of magnetic nanoparticles (NPs) play an important role in their properties. In particular, the bimagnetic NPs display useful and in many cases, more interesting properties than single-phase NPs. In this work, we prepared Fe3O4 and CoFe2O4 cube-like NPs and bimagnetic hard/soft (CoFe2O4/Fe3O4) and soft/hard (Fe3O4/CoFe2O4) nanocomposites (core/coating) using a facile and eco-friendly co-precipitation method that allows the synthesis of the cube-like NPs at temperatures near room temperature. The phase purity and the crystallinity of the NPs with a spinel structure were confirmed by the Xray diffraction and infrared spectra techniques. Transmission electron microscopy (TEM) images revealed that the NPs have a cubic-like shape with an average dimension of 20 nm. Energy dispersive X-ray analysis, Mossbauer spectroscopy and SQUID magnetic measurements indicated the co-existence of Fe3O4 and CoFe2O4 phases in nanocomposites. In addition, the hysteresis loops exhibited a single-phase behavior in the nano composites that indicates there is a good exchange-coupling interaction between the hard and soft magnetic phases. The CoFe2O4/Fe3O4 nanocomposites presented a larger saturation magnetization than the CoFe2O4 NPs that is effective for their use in magnetic hyperthermia. Finally, we studied the hyperthermia properties of samples in an alternating magnetic field with a frequency of 276 kHz and field amplitude of 13.9 kA/m. Our results showed that magnetic hyperthermia efficiency simultaneously depends on the composition of samples along with magnetic anisotropy and saturation magnetization.