Author : Erum Pervaiz and I.H.Gul

Gd3+ doped nanocrystalline Co-ferrites CoGdxFe2-xO4 (x =0.0 to 0.1) has been prepared by sol-gel auto combustion technique. Structural and morphology studies were performed using X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Indexed XRD patterns confirm the formation of pure cubic spinel phase. Average crystallite sizes ranges from 16 nm to 25 nm ±2. Lattice constant (a) and crystallite size D (311) increases with increase in Gd3+ concentration due to large ionic radii (0.94nm) of Gd3+ replacing Fe3+ (0.64nm ). FT-IR analysis shows the presence of two expected bands attributed to tetrahedral and octahedral metal oxygen vibrations. SEM images show the spherical morphology and uniform size distribution. Room temperature DC electrical resistivity decreases (~106) for x=0.025 then increases up to x=0.1 ~ (2.67×108) Ω-cm. Dielectric properties have been studied in the frequency range of 1 kHz to 5 MHz. Permittivity and tangent loss (tanδ) decreases with the substitution of Gd3+ in parent crystal structure and have values of 12.4 and 0.0160 at 5 MHz respectively. Complex impedance plots were further studied for complete contribution of grains and grain boundary resistances. Magnetic studies shows that magnetization (Ms) decreases with increase in Gd3+ concentration from 63 emu/gm to 27.26 emu/gm, thus the material is becoming low loss dielectric, highly resistive and soft magnetic due to Gd3+ doping.

Keywords: Rare earth ions, XRD, W-H plots, Dielectric properties, AC conductivity, magneto crystalline anisotropy

Article published in International Journal of Current  Engineering  and Technology, Vol.2,No.4 (Dec- 2012)