Dielectrically modified Nd³⁺ doped (Ni–Mn) based spinel ferrite Ni_0.5Mn_0.5Nd_xFe_2-xO₄ nanoparticles for energy storage applications

The neodymium doped Ni–Mn based spinel ferrites nanomaterials Ni_0.5Mn_0.5Nd_xFe_2-xO₄ with doping concentration of 0.00–0.20 were synthesized by sol gel auto-combustion method. All the samples in fine powder were annealed at 600 °C in a muffle furnace for 4 h to remove the impurities and absorbed gases. In XRD patterns, the obtained high intense diffraction peak at (311) is good evidence that the prepared materials are spinel ferrites. With the help of Scherer method, the crystallite size was calculated in nanometer ranging from 13 to 19 nm. Further, the calculated crystallite size was correlated with Williams's Hall, modified Scherrer and size strain plot (SSP) method. The study of surface morphology by scanning electron microscopy (SEM) revealed that some grains are non-uniform at different concentration of neodymium. Fourier transform infrared-spectroscopy (FTIR) analysis was used to study the relationship between transmittance and wavenumber. The pattern obtained from tetrahedral and octahedral site represents two frequency band v₁ and v₂. The electrical properties like dielectric constant, tangent loss, electric modulus and ac conductivity were studied by impedance analyzer in applied frequency range 1 MHz–3 GHz and result was explained by using Maxwell Wigner method. It was found that there are some relaxation peaks were observed at high frequency due to hopping of electrons. By using Vibrating sample magnetometer (VSM), the magnetic properties were studied in the applied magnetic field ranging from -3kOe to 3 kOe. The hysteresis loop shows the decreasing in retentivity (M_r), magnetization (M_s) and coercive field (H_c). In conclusion, these prepared materials are very useful for energy storage device applications.