Magnetically superior and easy to handle L10-FePt nanocrystals

Yamamoto, Shinpei; Morimoto, Yasumasa; Ono, Teruo; Takano, Mikio
July 2005
Applied Physics Letters;7/18/2005, Vol. 87 Issue 3, p032503
Academic Journal
We report synthesis of monodisperse L10-FePt nanocrystals that are not only superior in magnetism but also easy to handle through being dispersible in solvents. Thanks to a thick SiO2 coating, the thermal treatment needed to form the L10 structure can be done even at 900 °C without inducing coalescence and coarsening. The protecting shell was thereafter removed in a specific way that enabled us to recover the L10-FePt nanocrystals in a water dispersion. The SiO2-coated nanocrystals show a high coercivity of 18.5 kOe at room temperature in spite of their core size of only 6.5 nm in diameter, and the hysteresis loop of the water-dispersed nanocrystals, which were frozen under an external field, was almost rectangular indicating that their magnetic and structural orientation could be attained.


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