LAUSR

Abstract Co-precipitated and 800 °C annealed Ni x Cu 0.1 Zn 0.9- x Fe 2 O 4 ( x = 0.5, 0.6, 0.7) ferrite nano particles were studied by X-ray diffraction, FTIR and FC–ZFC techniques. The presence of Cu 2+ ions drastically affects the cation distribution which was obtained by Rietveld refinement. This cation distribution was utilized in interpreting the structural and magnetic properties. The variation in calculated tetrahedral and octahedral bond lengths ( R A , R B ) and oxygen parameter ( U ) as a function of Ni 2+ ion concentration are explained in terms of cation redistribution given by Rietveld refinement. The variation of tetrahedral and octahedral Fe–O vibrational frequencies observed in FTIR studies are in accordance with the change in R A and R B bond lengths. The metal – oxygen – metal bond angles calculated in the present studies indicates an increase in A – B super exchange interaction as Ni 2+ ion concentration is increased. The variation of blocking temperatures ( T B ) obtained from FC–ZFC studies are in accordance with that expected from Mossbauer studies. The magnetocrystalline anisotropy constant ( K ) calculated from T B values was found to increase as Ni 2+ ion concentration is increased. The K value was found to increase for a given Ni 2+ ion concentration as the temperature is decreased. The coercive field ( H c ) values estimated at 10 K were found to decrease as Ni 2+ ion concentration is increased.