Optimization of structural, dielectric, and magnetic properties of nanocrystalline copper doped spinel ferrites

•The samples Ca0.5Ba0.5-xCuxFe2O4 (x = 0.00, 0.125, 0.250, 0.350, 0.500) spinel ferrites prepared by sol–gel auto combustion method results in enhanced structural, dielectric and magnetic properties.•XRD patterns of samples indicate that the peaks match well with the standard patterns of the spinel ferrites.•Crystallite size lies in the range of 37.43–50.07 nm.•At room temperature the conductivity of ferrites is due to impurity, as at higher temperature conductivity is occurring through polaron hopping.•Dielectric constant according to Maxwell–Wagner model the dielectric substance contains with heterogeneous structure thought that good conducting grains separated by highly resistant thin grain boundaries.•Dielectric losses very essential part of the sum core loss in magnetic materials, According to Hudson theory.