Microwave assisted hydrothermal synthesis of (Fe,Co) 3 O 4 nanoparticles in the presence of surfactants and effects of Co/Fe ratio on microstructure and magnetism

Abstract Microstructure and magnetic properties of nanoparticles can be tailored by optimising the synthesis procedure and changing chemical composition. In this study, a two-step procedure, i.e., coprecipitation in the presence of PEG 300 followed by microwave assisted (MW) hydrothermal synthesis, was introduced to obtain Co x Fe 3- x O 4 ( x  = 0, 0.1 and 0.2) nanoparticles. It was found that with the increase of Co content, particle/crystallite size increased, with significant change of coercivity (H c ). The mixed samples of Co x Fe 3- x O 4 ( x  = 0.1 and 0.2) were magnetically harder in comparison with Fe 3 O 4 . Тhe H c of Fe 3 O 4 was 91 Oe, while for Co 0.10 Fe 2.90 O 4 and Co 0.20 Fe 2.80 O 4 , H c was 256 Oe and 1070 Oe, respectively. Saturation magnetisation (M s ) of mixed samples also increased up to 6% compared to Fe 3 O 4 . A special effort was devoted to study the effects of introducing different surfactants (PEG 300, PEG 4000 or SDS) during the synthesis procedure in order to improve morphological and microstructural properties of CoFe 2 O 4 nanoparticles. The influence of surfactants on physical/chemical properties of nanoparticles is discussed.