Mossbauer, x-ray and magnetization studies of Ni0.5Zn0.5AlxFe2-xO4 system

The structural and magnetic proper-ties of the mixed spinel system Ni0.5Zn0.5AlxFe2-xO4 (x=0.0,0.2,0.4,0.6,0.8 and 1.0) have been investigated by X-ray diffraction, magnetization and Mossbauer measurements. The variation of Mossbauer, parameters, lattice parameters and crystalline size of the products formed with variation in the composition of Fe and Al ratio has been studied. The studies confirm the formation of nano-size ferrite particles. It is observed that lattice parameters decrease, with increasing aluminium concentration. A ferromagnetic relaxation occurs when x is increased to 0.6, which is followed by weak paramagnetic transition. With further increase of x to 1.0 the system again shows weak ferromagnetism. The decrease in magnetic hyperfine field with increase in Al concentration has been explained on the basis of super transferred hyperfine field. The variation of the saturation magnetic moment per formula unit measured at 300 K decreases with Al concentration x, suggesting the decrease in ferromagnetic behaviour. These observations. indicate the existence of a non-collinear structure in a nano-particles ferrite system. The non-collinear structure in this system is also verified by Neel's two sub-lattice model.