摘要
Lanthanum doped nickel-cobalt nano ferrites with chemical formula Ni_(0.5)Co_(0.5)LaxFe_(2-x)O_(4)(x=0.05,0,10,0.15 and 0,20) were prepared using a simple sol-gel auto combustion method.The basic structural properties were determined by X-ray diffraction method and the formation of single phased spinel ferrite was confirmed.The crystalline size decreased from 25 to 11 nm and lattice parameter a increases with increase of La doping.The surface morphology of these ferrites was observed by field-emission scanning electron microscopy(FESEM) and agglomerated irregular grains are observed with increase of the rare earth element La doping.Energy-dispersive X-ray spectroscopy(EDX) result confirms the presence of the required elements.The Fourier transform infrared spectroscopy(FTIR) spectrum indicates the formation of the spinel ferrite structure with M-O bonds.Optical direct band measurements from ultraviolet-visible spectroscopy(UV-Vis) spectroscopy indicate that the direct band gap decreases from 1.39 to 1.19 eV for x=0.05 to x=0.15,then increases to 1.28 eV for x=0.20.The room temperature magnetic properties of these ferrites were studied by a vibrating sample magnetometer(VSM).The enhanced saturation magnetization of 49.73 emu/g is observed for x=0.10 and then saturation magnetizations are gradually decreased for x=0.15 and x=0.20.Interestingly the remanent magnetization and coercivity also follow the same trend.
