Superparamagnetic CoFe2O4 prepared via a modified oxalate method

Abstract

Abstract The modified oxalate precursor method was used for the preparation of nanocrystalline CoFe2O4. Structural investigations of as-produced powders performed by means of high-resolution transmission electron microscopy and X-ray diffraction revealed an average particle size of 8 nm. The nanocrystallites are pure CoFe2O4 and present a well crystallized spinel structure with lattice constant of 8.3583 Å. The particles are superparamagnetic exhibiting a blocking temperature around room temperature. The magnetization and the coercive field values obtained at 9 T are 56.8 emu · g−1 and 17.0 kOe (at 4.2 K), respectively. The crystalline anisotropy determined from the coercive field as a function of temperature is 8.0 × 105 J · m−3, which is much higher than that of bulk materials.