Graduate Research and Discovery Symposium (GRADS)


Synthesis and characterization of Multi-dopant Ferrite Magnetic Nanoparticles with Designed Structures

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Nonstoichiometric ferrite nanoparticles have drawn attention on the tunability of the magnetic properties by controlling the composition. We adopted the extended LaMer technique to synthesize multi-dopant ferrite nanoparticles with core-shell structure by controlling the pumping rate. The synthesis consists two steps: 1) synthesis of oleate precursors, and 2) continuous injection synthesis of particles. Cobalt oleate and nickel oleate were mixed separately with iron oleate in a volume ratio of 1:2, respectively, to give a cobalt ferrite precursor and nickel ferrite precursor solutions. The two precursor solutions were injected respectively with controlled pumping rate (Fig. 1), and cobalt ferrite/nickel ferrite core-gradient shell nanoparticles were then produced with continuous growth (Fig 2). Nanoparticles with same core size and shell thickness were made. Samples with low, medium, and high gradients were compared with a control with no gradient. TEM (Transmission Electron Microscopy) results showed a well-controlled size with a mean diameter of 10 nm and standard deviation of 1 nm. The elemental distribution throughout the particle was analyzed by EELS (Electron Energy Loss Spectroscopy) to confirm the existence of core-gradient shell structure. Physical properties, such as saturation magnetization, blocking temperature, and effective anisotropy were then measured and calculated based on VSM (Vibration Sampling Magnetometry) and ZFC-FC (Zero Field Cooling-Field Cooling) measurements.

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