MAGNETIC BEHAVIOUR OF NANOPARTICLES OF NI0.5CO0.5FE2O4 PREPARED USING TWO DIFFERENT ROUTES

Abstract

Literature reports on bulk sample of the ferrite Ni 0 . 5 Co 0 . 5 Fe 2 O 4 confirm a complete inverse spinet structure. On site occupancy and magnetic anisotropy on nano-particle samples of the titled ferrite prepared usingtwo different routes - a wet chemical co-precipitation process and sol-gel method have been studied. Estimated average particle sizes of the two samples (referred to as NCWET and NCSOL) are ∼75A and ∼190A respectively. Small angle neutron scattering measurements made on the fluid sample comprising the sample prepared by wet chemical process gives median size ∼77A with standard deviation σ = 0.60. Mosshauer studies at 300K show that the two ferrite samples maintain inverse spine structure even in nanocrystalline state. Magnetization and Mosshmier measurements show that part of the sample in both the cases is in superparainagnetic state. Magnetic anisotropy is larger in the nano-particle state and surface spin disorder also contributes to this.