Dielectric Properties and Magnetodielectric Effect of Co_1−xCr_xFe₂O₄

This research investigates the dielectric and magnetodielectric properties of spinel-type Cr³⁺-substituted cobalt ferrites with the general formula Co_1−xCr_xFe₂O₄ (x = 0.000, 0.125, 0.250, 0.375, 0.500) over a wide range of temperatures and frequencies. The samples are synthesized by solid-state reaction via ball milling for 12 h and sintering at 1200°C. The grain size estimated from scanning electron microscopic images shows a decreasing value with increased Cr³⁺ content. The compactness of grain size reduces the dielectric behavior as analyzed from the frequency-dependent complex permittivity. The temperature-dependent real permittivity reveals that the x = 0.125, 0.250, and 0.375 samples behave as relaxor ferroelectric compounds, whereas the x = 0 and 0.5 samples behave as diffuse ferroelectrics. Detailed analysis of the electric modulus from the complex permittivity reveals the grain boundary and grain contribution, respectively. Around the relaxation frequency, a notable magnetodielectric response (maximum 6.5%, in the presence of 1 T applied magnetic field at room temperature) is found for all samples.