Using a combination of X-ray diffraction, room temperature/low temperature Mössbauer studies and d.c. magnetization, the structural and magnetic properties of nano-sized Cu 0•25 Co 0•25 Zn 0•5 Fe 2 O 4 , prepared using the coprecipitation method at different seeding temperatures, have been studied. Formation of α-Fe 2 O 3 in these samples is observed to be very sensitive to the seeding temperature and is totally suppressed at a seeding temperature of 333 K. These results are explained in terms of the rate of coprecipitation of the different components as a function of temperature. Since α-Fe 2 O 3 is antiferromagnetic, the presence and quantity of this impurity is also observed to deteriorate the overall magnetic properties of the spinel phase.