Magnetik Nanoparçacıkların Magnetik Özellikleri ve Spin Dinamiği
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In this thesis three types of samples including oleic acid and oleyl amine coated spherical magnetite (Fe3O4) nanoparticles and gold-magnetite (Au-Fe3O4) hybrid nanoparticles in dimer and coreshell geometry has been synthesized by chemical methods. The structural characterization of synthesized samples has been made by using X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Fourier Transform Infrared Spectroscopy (FTIR) techniques. The mean diameters for synthesized nanoparticles have been determined as 7,5 nm for Fe3O4 nanoparticles and 11,0 nm and 14,0 nm for Au-Fe3O4 dimer and coreshell hybrid nanoparticles, respectively. The optical properties of samples have been investigated by analyzing optic absorption spectra collected in UV-visible region, whereas magnetic properties have been determined by means of ac and dc magnetic susceptibility measurements using Superconducting Quantum Interference Device (SQUID) magnetometry technique. It has been observed that the samples show typical superparamagnetic behaviour with magneto-thermal irreversibility and blocking phenomena.