Effect of Gd³⁺ ion distribution on structural and magnetic properties in nano-sized Mn-Zn ferrite particles

Nanoparticles of Gd³⁺ ions doped Mn_0.5Zn_0.5GdxFe_2-xO₄ (x = 0.1, 0.2, 0.3, 0.4) mixed ferrite were prepared using chemical co-precipitation method. The X-ray diffraction measurements confirmed the formation of a cubic spinel structure. The structural parameters like crystallite size, lattice parameter and strain induced have been calculated. The lattice parameter increases with the increase in Gd³⁺ ion concentration and shows non linear behaviour. HRTEM investigation confirms the nano size formation of the Gd doped Mn-Zn ferrite nanoparticles. EPR was used to evaluate resonance peak intensity, Lande's splitting factor (g value), peak to peak line width (ΔH_p-p), spin concentration (N_s) and relaxation time (t_s). Line width, line intensity, relaxation time and spin concentration increase with Gd³⁺ ions doping (forx=0.1 to x=0.3) and then decrease for x-0.4, whereas the g value shows the reverse trend for the same composition. IR spectra shows two strong absorption bands at 570 cm^-1 and 416 cm^-1 of tetrahedral and octahedral bond stretching respectively in all the samples. IR spectrum also shows that Gd³⁺ occupies the octahedral B-sites. Magnetic parameters such as saturation magnetization (M_s), remanence (M_r) and coercivity (H_c) were measured by search coil method. The value of saturation magnetization increases from 29.94 emu/gm for x=0.1 to 46.01 emu/gm for x=0.4.