Magnetic studies of CuFe₂O₄ nanoparticles prepared by co-precipitation method

Cu-ferrite nanoparticles were synthesized by co-precipitation method and were annealed at different temperatures ranging from 400 to l000°C in air for 4 hours. The as-prepared sample and the sample annealed at 400°C showed small peaks of cubic Cu-ferrite in X-ray diffraction studies. For the intermediate temperature 600°C, some additional peaks of α-Fe₂O₃ were observed. As the annealing temperature increased further only tetragonal Cu-ferrite peaks were observed. In all the samples some traces of CuO was noted. Grain size was increased from 2lnm for the as prepared sample to 42nm for the sample annealed at l000°C. Spontaneous magnetization value was found to be very small for the as prepared sample and it was increased monotonically with the increase in annealing temperature. Maximum magnetization of 29.7emu/g was observed at 300K for the sample annealed at l000°C. The remanent magnetization was increased with the increase in annealing temperature up to 900°C and then decreased whereas for the coercivity a peak was observed for the sample annealed at 800°C. The highest coercivity of l402 Oe was observed at 300K for the sample annealed at 800°C. As the measurement temperature decreased from 300K to 60K, magnetization and coercivity values were increased. The observed magnetic behaviour may be understood on the basis of phase transformation, grain growth with the increase in annealing temperature and reduced thermal energy at low measurement temperature.