Almost spherical CoFe2O4 nanocrystals with a narrow size distribution centered around 2.5(5)nm, uniformly dispersed in an amorphous SiO2 matrix have been prepared by high energy ball milling followed by thermal treatment at 900degreesC. Mossbauer spectra show the presence of CoFe2O4 nanoparticles in the superparamagnetic state at 293 K and mainly in the blocked state at 77 K. This is confirmed by ZFC/FC measurements giving evidence of a distribution of blocking temperatures, centered at 50 K.
Magnetic Properties of Nanocrystalline CoFe2O4 Dispersed in Amorphous Silica
CONGIU, FRANCESCO;CONCAS, GIORGIO;ENNAS, GUIDO;FALQUI, ANDREA;
2004-01-01
Abstract
Almost spherical CoFe2O4 nanocrystals with a narrow size distribution centered around 2.5(5)nm, uniformly dispersed in an amorphous SiO2 matrix have been prepared by high energy ball milling followed by thermal treatment at 900degreesC. Mossbauer spectra show the presence of CoFe2O4 nanoparticles in the superparamagnetic state at 293 K and mainly in the blocked state at 77 K. This is confirmed by ZFC/FC measurements giving evidence of a distribution of blocking temperatures, centered at 50 K.
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