Evidence of Weak Ferromagnetism, Space Charge Polarization, and Metal to Insulator Transition in Dy-Doped CaMnO3

The effect of Dy doping on CaMnO3 (CDMO) has been thoroughly investigated. The room-temperature structure, low-temperature magnetic transitions, and high-temperature electrical properties of CDMO were studied using X-ray diffraction, magnetization, and dielectric techniques. The CDMO exhibits an orthorhombic structure with Pnma symmetry. The low-temperature magnetic susceptibility data show the ferromagnetic domains embedded in the antiferromagnetic structure (G-type), and it confirms the Neel temperature (T-N) approximately 55 K. Temperature-dependent dielectric data measured using a few selected frequencies show a high dielectric constant similar to 29,108,808 at 1 kHz. The presence of a high dielectric constant at the lower frequency side can be attributed to the space charge polarization (SCP) and compositional disorder (heterogeneity) in the compounds. The impedance cole-cole plot shows a depressed semicircle; mathematically these data were fitted by the Kohlrausch-Williams-Watt model. From this model obtained two mechanisms: (i) the electric modulus divulges the CDMO ceramic tails the Non-Debye type of relaxation and (ii) the electric modulus peak shifting evidence the charge carrier mobility from long range to short range. High-temperature dielectric, resistivity, and conductivity data show a clear anomaly around 461 K, owing to metal to insulator transition.