Structural, dielectric and magnetic properties of Gd substituted manganese ferrite nanoparticles

Gd³⁺ ion-substituted manganese ferrite nanoparticles with the chemical formula MnGd_xFe_2-xO₄ (x = 0.0, 0.05, and 0.1) were synthesized by sol–gel auto combustion method. Thermal stability of the as-prepared sample was analyzed using thermo gravimetric and differential thermal analysis (TG–DTA) and the result reveals that the prepared sample is thermally stable above 300 °C. Structural and morphology studies were performed using powder x-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Indexed PXRD patterns confirm the formation of pure cubic spinel structure. The average crystallite sizes calculated using Sherrer's formula decreased from 47 nm to 32 nm and lattice constant was enhanced from 8.407 Å to 8.432 Å. The FTIR spectrum of manganese ferrite shows a high frequency vibrational band at 564 cm⁻¹ assigned to tetrahedral site and a low frequency vibrational band at 450 cm⁻¹ assigned to octahedral site which are shifted to 556 cm⁻¹ and 439 cm⁻¹ for Gd³⁺ substitution and confirm the incorporation of Gd³⁺ into manganese ferrite. SEM analysis shows the presence of agglomerated spherical shaped particles at the surface. Room temperature dielectric and magnetic properties were studied using broadband dielectric spectroscopy (BDS) and vibrating sample magnetometry (VSM). Frequency dependent dielectric constant, ac conductivity and tan delta were found to increase with Gd³⁺ ion substitution. The measured values of saturation magnetization decrease from 46.6 emu g⁻¹ to 41 emu g⁻¹ with increase in Gd³⁺ concentration and coercivity decreases from 179.5 Oe to 143 Oe. (paper)