| Summary: | 碩士 === 東海大學 === 物理學系 === 98 === Bulk FeSix (x= 2, 2.5, 3.8, 6) were fabricated by Arc furnace. FeSi2.5 are pure α phase, others are the mixture of α-FeSi2 and Si. The nanoparticles were fabricated by ND:YAG pulse laser deposition using α phase or β phase target. The nanoparticles are pure α phase or mixture of α phase and silicon by using α phase target. But β phase nanoparticles were grown only using laser ablation of the β phase target by laser of 266nm or 355nm. The structure and distribution of size were examined by X-ray diffraction patterns and HR-TEM. The magnetic properties of bulks and nanoparticles are measured by SQUID. Although Bulk FeSix (x= 2, 2.5, 3.8, 6) are practically nonmagnetic. All nanoparticle samples (diameter between 7 and 15nm) appears the character of superparamagnetism with blocking temperature ranging from 2.5K to 10K. There behaviors are similar to the β-FeSi2 nanoparticle[1]. The concentrations of magnetic Fe were estimate by Curie constant. By assuming 2μB per magnetic Fe, only about 2 % ~ 11 % of magnetic Fe existed in these samples. The magnetism of the α phase may come from chemical disorder as occurrence of β-FeSi2 nanoparticles.
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