Microstructural, dielectric, magneto-electric and optical properties of single phase Ca3CoMnO6

Type II intrinsic multiferroics oxide Ca3CoMnO6 (CCMO) having collinear spin ordering and non-zero polarization is a fascinating compound from the view point of fundamental and technological applications. Room temperature properties of Ca2.7Sr0.3CoMn1-xFexO6 ceramics with dilute Fe doping (x) have been investigated. Rietveld refinements of X-ray diffraction data confirmed single rhombohedral phase with R-3c space group for all the samples. Frequency dependent dielectric properties with low loss tangents measured in frequency range of 1 MHz to 1 GHz, showed an increase in the real permittivity upon Fe doping within the entire frequency range; which is attributed to doping induced optimal modification in Co/Mn ratios. Room temperature ME coupling coefficient of the order of 1.7 mV/cm Oe for pure CCMO is achieved and the mechanism is explained through exchange striction model. It suggested that the dilute Fe substitution (or Mn deficiency) break the inter chain interactions to some extent, in otherwise, quasi collinear magnetic chain structure. Kubelka-Munk function was applied to analyse the optical measurements, which revealed an increase in reflectance and refractive indices with doping of Fe into pure CCMO. Consequently, the optical band gaps were found to systematically decrease from 2.25 eV to 1.80 eV upon Fe doping at the Mn-site.