Substitution effects of La3+ ions on the structural and magnetic properties of Co2Y hexaferrites synthesized by sol-gel autocombustion method

Y-type hexaferrite Sr2Co2LaxFe12-xO22 (x = 0.0, 0.05, 0.10, 0.15, 0.20) powders have been synthesized using the sol-gel autocombustion method. Differential Scanning Calorimetry, Thermogravimetry, Fourier Transform Infra-Red spectroscopy, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and vibrating sample magnetometery were used to investigate the samples. XRD patterns confirm the formation of Y-type hexaferrite phase. SEM patterns show that mostly grains exhibit rod shape and some appear in the form of hexagonal platelet shape. The rod or rice shape hexaferrite may be used in catalysis, information storage, surface enhanced Raman scattering, imaging and sensing. The samples with hexagonal platelet-like shape particles may be suitable as microwave absorbing materials. The energy dispersive X-ray spectroscopy spectrum shows the presence of dissolved reactants Sr, Co, La and Fe. The saturation magnetization (M-s) calculated using the law of approach to saturation decrease with the increasing of lanthanum (La3+) contents. The decrease in 'M-s' may be because of magnetic dilution and spin canting and hence reduction in the super-exchange interactions. The retentivity (M-r) and coercivity (H-c) enhance with the increase of La3+ contents. The enhancement in coercivity from 193 to 598.6 Oe may be because of increase in the porosity of samples with the increase of La3+ contents. The coercivity of the synthesized materials is few hundred oersteds (Oe), which may be suitable for security, switching, sensing, high frequency applications and is also favorable for electromagnetic materials.