Dielectric properties of magnetic grains in CoFe1.95Ho0.05O4 spinel ferrite

► Dielectric properties of ferromagnetic grains in single and multi-domain regimes. ► Modulus formalism identified dielectric relaxation at grain and grain boundaries. ► Connectivity between dielectric properties and magnetic domain structure transformation. ► The results are interesting from the application point of view. ► This ferrite material showed sufficiently large dielectric constant and low loss.