Enhancement in magnetic, dielectric properties, and specific capacitance of Mn-substituted Zn ferrite for energy storage devices

Manganese-doped zinc ferrite nanoparticles (Mn_xZn_1−xFe₂O₄) with compositions x = 0.0, 0.3, 0.5, 0.7, and 1.0 were synthesized using the chemical co-precipitation method. The synthesized samples were thoroughly characterized using X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, high-resolution transmission electron microscopy (HRTEM), vibrating sample magnetometer (VSM), electron paramagnetic resonance (EPR), dielectric analysis, and cyclic voltammetry (CV). The lattice constant calculated using XRD decreases with manganese content. FTIR spectra exhibited characteristic bands of spinel ferrites. Doping of manganese ions strengthens the tetrahedral and octahedral sites, leading to higher wavenumbers and force constants. HRTEM images reveal the spherical morphology of the synthesized particles. VSM measurements showed an increase in maximum magnetization up to sample Mn_0.7Zn_0.3Fe₂O₄, which has a magnetization of 42.74 emu/g. The resonance field (H_r) decreases with doping due to the stronger magnetic interactions induced by manganese doping. Dipolar interactions become more prominent at higher Mn concentrations, which leads to line broadening and reduced spin relaxation times. The dielectric constant is analyzed with varying frequency and it shows frequency-dependent behavior. Specific capacitance was recorded at different scan rates using the CV technique and sample ZM7 shows the most promising potential for supercapacitative applications with a specific capacitance of 690.31 F/g at 10 mV/s. The study underscores the potential of manganese doping to tailor the structural, magnetic, and dielectric properties of zinc ferrite for applications in energy storage, spintronics, and catalysis.