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Ferromagnetic and superparamagnetic ordered nanoparticles configurations
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Contract no: 71-119 / 2007
Contact: Dr. Ioan-Ovidiu Pana |
Results Stage I Stage II Stage III Stage IV Stage IV
Laboratory method for synthesis of ferromagnetic nanoparticles based on FePt alloy with L10 phase. The poliol method is based on the reduction of the metallic salts to metallic particles using diol and polyalcohol. In our case the method consisted in the reduction of acetylacetonate of platinum(II) in the same time with the decomposition of pentacarbonil iron (Fe(CO)5) in controlled atmosphere (argon). Structural characterization The crystal structure of the FePt nanoparticles was determined by XRD. The obtained diffractograms of the untreated samples indicates the existence of a disordered phase with a cubic face centered structure, and within the structure the Fe atoms substitute randomly the Pt atoms and vice versa. By thermal treatment the Fe and Pt atoms rearrange in a structure with long order, tetrahedral face centered. This structure can be interpreted as a supra-structure which is formed by the natural arrangement of the Fe and Pt atoms in alternative crystallographic planes. This phase is stabilizing at temperatures above 500°C. For the synthesis method of thermal treatment in controlled atmosphere of argon , it was concluded that the procedure obtains the ordered L10 phase with an inappropriate reproductibility. The XRD diffractograms of two sets of the same sample, using the thermal treatment in argon atmosphere, indicates a good structural reproductibility.
Magnetic characterization For the magnetic characterization, at room temperature, the main characteristics of these nanoparticles are the high coercitive field (~5000 – 8000 Oe) and the high saturation magnetization (~50 emu/g). It can be concluded that the synthesis method based on thermal treatment in argon gas, it can be used to obtain high values of the coercitive field and a good reproductibility of the magnetic behavior (< 5%).
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