Precursor of nanocrystalline Co0.35Mn0.65Fe2O4 was synthesized by solid-state reaction at low heat using CoSO4 center dot 7H(2)O, MnSO4 center dot H2O, FeSO4 center dot 7H(2)O, and Na2C2O4 as raw materials. Nanocrystalline Co0.35Mn0.65Fe2O4 with spinel structure was obtained via calcining the precursor. The precursor and its calcined products were characterized using TG/DSC, FT-IR, XRD, SEM, EDS, and vibrating sample magnetometer. The results showed that the precursor dried at 353 K was a mixture consisted of CoC2O4 center dot 2H(2)O, MnC2O4 center dot 2H(2)O, and FeC2O4 center dot 2H(2)O. However, when the precursor was calcined at 623 K for 2 h, highly crystallization Co0.35Mn0.65Fe2O4 [space group R-3 m (166)] was obtained with a crystallite size of 22 nm. Magnetic characterization indicated that the specific saturation magnetization of Co0.35Mn0.65Fe2O4 obtained at 773 K was 66.14 Am-2/kg. The thermal process of precursor experienced two steps, which involves the dehydration of the waters of crystallization at first, and then decomposition of Co0.35Mn0.65Fe2(C2O4)(3) and formation of crystalline Co0.35Mn0.65Fe2O4 together. Based on the Kissinger equation, the values of the activation energy associated with the thermal processes of the precursor were determined to be 78 and 146 kJ/mol for the first and second thermal process steps, respectively. (C) 2011 Elsevier B.V. All rights reserved.