Effects of Ce–Co substitution on structural, magnetic and dielectric properties of M-type barium hexaferrite nanoparticles synthetized by sol–gel auto-combustion route

M-type Ce–Co substituted barium hexaferrite nanoparticles were synthesized by sol–gel auto-combustion route. The general formula of ferrites was Ba_1−xCe_xFe_12−xCo_xO₁₉ in which the x was considered to be: x = 0, 0.1, 0.2, and 0.3. The formed phases in the samples were characterized by using X-ray diffraction, Fourier transform infrared spectroscopy, Mössbauer spectroscopy and vibrating sample magnetometer. The results indicated that an increase in substitutional ion amount caused to decrease vibration frequencies of Fe–O band in the tetrahedral site due to the substitution of heavier Co²⁺ ion for Fe³⁺ ion in the tetrahedral site. Moreover, some of Ce³⁺ ions was transformed to Ce⁴⁺ and consequently with change in ionic radius from 1.02 to 0.87 Å. It seems to us that some of this ion substituted for Fe³⁺ in the octahedral 12k site. The data showed that the saturation magnetization was increased from 41.25 to 46.03 emu/g, and coercivity decreased from 5,500 to 4,700 Oe, with increasing x from 0.0 to 0.2. The network analyzer results showed that the dielectric constant and dielectric loss decreased with increasing Ce–Co substitution.