The nanoparticles of the spinel ferrite system Ni1-xMnxFe2O4 with x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0 were prepared using the auto combustion flash method technique, by using the nitrates as cations source and urea as a fuel agent for combustion. The XRD pattern validates the formation of cubic spinel structure of Ni1-xMnxFe2O4 nanoparticles and traces of hematite phase. By increasing the annealing temperature, the lattice parameter and crystallite size were increased. At various frequencies, the dielectric properties and initial permeability were measured as a function of temperature. The DC resistivity was found to have a linear relationship with temperature, with two regions and one break point at Curie temperature (TC). SEM and TEM analyses are used to investigate the morphology of the samples, as well as the size and shape of the crystallites. The samples' morphology revealed the formation of a uniform and spherical structural distribution. The material transfer to multiferroic at high Mn content accordingly the ferroelectric and ferrimagnetic properties appear, which give the ability of the material to become magnetoelectric material.