Magnetic Properties of Nanoparticles Surface-Modified with Oleic Acid

Oleic-acid-modified magnetite nanoparticles were synthesised by coprecipitation and characterised using structural, spectroscopic, and magnetic methods. X-ray diffraction and transmission electron microscopy confirmed magnetite cores with an average size of approximately 11.5 nm, while Fourier transform infrared spectroscopy demonstrated the chemisorption of oleic acid. Mössbauer spectroscopy revealed superparamagnetic relaxation and collective magnetic interactions. Low coercivity and a blocking temperature of about 160 K indicate predominantly superparamagnetic behaviour at room temperature.