Characterization of CoCrFeO₄ Nanocrystals Preparedby a Sol-Gel Method

CoCrFeO₄ nanocrystals have been synthesized using a sol-gel method. The specimen has an average grain size of 8.1 nm. The zero-field-cooled and field-cooled curves show a superparamagnetic transition occurring at a blocking temperature of T_B ≈ 249 K. The increase in coercivity of CoCrFeO₄ nanocrystals with the decreasing temperature has been detected below the blocking temperature and could be explained by the Stoner-Wohlfarth theory. The temperature dependence of saturation magnetization shows that Bloch's law holds but with the Bloch exponent lower than the bulk value.