Study on New Magnetic Nanoparticles

点击翻译按钮获取中文摘要

Magnetic properties of transition metal-oxide nanoparticles were investigated. Magnetization measurements were already reported for Ni(OH)2 monolayer nanoclusters (Ni-MNC), and additionally, in order to confirm their two dimensionality local structure was studied by XAFS analyzes.NiO nanoparticles were produced by annealing above mentioned Ni(OH)2. Their diameters were estimated between 2 and 6 nm. In the magnetization measurements superparamagnetic or ferromagnetic behaviors were observed though NiO bulk crystal shows antiferromagnetism.y-Fe203 and α-Fe2O3 nanoparticles were confirmed for Fe-O systems depending on annealing temperature and annealing time. Large coersive force of about 1 kOe was found for the sample annealed at 1023 K for 10 hours. This material could be expected to realize high density magnetic recording media. This result was reported by Nikkan Kogyo Newspaper in 2001.In order to improve mangnetic parameters of Fe2O3 nanoparticles, Co ions were doped into iron oxide nanopartcles. Mole ratio of Co/Fe was varied between 0.05 and 0.7. Under the measuring temperature of 100 K, coersivity began to increase drastically as the amount of Co ion increased, however, after the largest coersivity was observed near 0.4 of Co/Fe ratio, no larger coersivity could be found and it rather decreased in higher concentration.