| Summary: | 碩士 === 東海大學 === 物理學系 === 94 === The bulk CeAl4 undergoes a ferromagnetic transition at TC = 6.2 K,
follow by an antiferromagnetic ordering at TN = 3.2 K . The CeAl4 nanoparticles was fabricated by pulsed-laser deposition methods.By controlling carefully the conditions , including gas pressures , laser power and temperature of substrate, the CeAl4 nanoparticles were fabricated with sizes between 10 and 30 nm .No impurity phase can be detected by X-ray diffraction patterns . The magnetic behavior of nanoparticles have been measured by SQUID between 2 K and 300 K.We find that when the particles’ size was reduced , the antiferromagnetism will be depressed . A typical behaviors of superparamagnetism below 6 K . show that the sample remain on ferromagnetic state . The small curie constant of nanoparticles , which was fabricated under 0.02 torr He gas ,was about 33% of the bulk . This imply that a certain degrees of demagnetization of Ce ions in nanoparticles .
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