Sol-gel synthesized CoFe2-xGdxO4:SiO2 nanocomposites for structural, thermal and magnetic investigation

Silica embedded cobalt ferrite CoFe 2-x Gd x O 4 :SiO 2 nanocomposites (x = 0.00, 0.025, 0.050, 0.075, 0.1) were synthesized successfully by sol-gel method. These fine powder form samples were further heat treated at temperature 750 °C and 1000 °C in muffle furnace for 2 h. A steady increase in lattice parameter and strain is observed in the range 8.375–8.489 Å and 0.00153–0.008 respectively with raising Gd 3+ ion content from 0.00 to 0.10 in samples annealed at 1000 °C. Appearance of bands in FTIR spectra at 860.09 cm −1 , 586.57 cm −1 and an array of 559–580 cm −1 are contributed by Si–O–Fe vibrations and absorption bands of Gd 3+ respectively. Further, TEM results demonstrate better uniformity, smaller size and much narrower distribution of particles at higher concentration of Gd 3+ ions and annealing temperature. No weight loss was observed beyond 750 °C observed by TGA analysis confirmed about full decomposition of precursors and formation of stable structures of CoFe 1.95 Gd 0.050 O 4 :SiO 2 and CoFe 1.9 Gd 0.1 O 4 : SiO 2 . Appreciable variations in important parameters like saturation magnetization (Ms), residual magnetization (Mr), coercivity (Hc) and anisotropy constant (K) by the Gd 3+ ions doping concentration in silica embedded CFO nanocomposites are determined. The drop in Ms could be due to surface dipoles disorderness induced microstrain by doping with larger Gd 3+ radii (0.94 Å) than Fe 3+ ions (0.67 Å). It may also be understood due to reducing effect on inter-sub lattice exchange energy between Co-O-Gd and Co-O-Fe with respect to Fe-O-Fe interactions in our prepared samples. These tailor-made magnetic materials are promising for memory device, gas sensing, magnetic drug delivery, spintronics and DNA separation properties. • XRD analysis revealed better-quality CoFe 2-x Gd x O 4 : SiO 2 for annealed at 1000 °C than 750 °C. • TEM analysis show nanoparticles with improved homogeneity, small size, and narrower size distribution. • Magneto crystalline anisotropy increases with Gd 3+ reveals strong interactions in Gd 3+ doped silica Co-ferrites nanoparticles. • TGA confirmed stable structure of CoFe 1.95 Gd 0.05 O 4 :SiO 2 and CoFe 1.9 Gd 0.1 O 4 :SiO 2 beyond 750 °C.