Polarization and Ni content effects on structural properties, electrical conductivity, complex impedance and dielectric constant of Co-Mg-ferritesR. Jemaï, R. Lahouli, H. Rahmouni, S. Hcini and K. KhirouniEur. Phys. J. Plus, 133 10 (2018) 410DOI: https://doi.org/10.1140/epjp/i2018-12209-5