Effect of Grain Size on Structural and Magnetic Properties of CuFe $_{2}$ O $_{4}$ Nanograins Synthesi

CuFe₂O₄ nanograins have been prepared by the chemical co-precipitation technique and calcined in the temperature range of 200-1200°C for 3 h. A wide range of grain sizes has been observed in this sintering temperature range, which has been determined to be 4 to 56 nm. Formation of ferrite has also been confirmed by FTIR measurement through the presence of wide band near 600 and 430 cm^-1 for the samples in the as-dried condition. Systematic variation of wave number has been observed with the variation of the calcination temperature. B-H loops exhibit transition from superparamagnetic to ferrimagnetic state above the calcination temperature of 900°C. Coercivity of the samples at lower calcination temperature of 900°C reduces significantly and tends towards zero coercivity, which is suggestive of superparamagnetic transition for the samples sintered below this temperature. Frequency spectrum of the real and imaginary part of complex initial permeability have been measured for the samples calcined at different temperature, which shows wide range of frequency stability. Curie temperature, T_c has been measured from temperature dependence initial permeability at a fixed frequency of 100 kHz. Although there is small variation of T_c with sintering temperature, the reduction of permeability with temperature drastically reduce for lower sintering temperature, which is in conformity with the change of B-H loops with the variation of sintering temperatures.