Improved magnetoelectric coupling of Co-Ti substituted barium hexaferrite at room temperature and related electrical investigations

This paper reports a systematic study of the electrical, multiferroic and magnetoelectric coupling properties of Co-Ti substituted Barium hexaferrites, having the chemical composition BaFe12-2xCoxTixO19 12-2x Co x Ti x O 19 (x = 0-2.0; in steps of 0.5), synthesized using the sol gel auto-combustion method. X-ray Diffraction (XRD) studies and Rietveld refinement confirmed the successful incorporation of Co-Ti ions in the hexaferrite lattice with all the samples displaying Pb63/mmc space group single phase structure. Scanning Electron Microscope (SEM) images revealed the inhibition of crystal growth in a particular direction with Co-Ti substitution. The conduction mechanisms of the samples were analysed from the conductivity measurements and were found to follow Jonschers power law. The complex impedance spectroscopy analysis and the Cole-Cole plot fitted diagrams of the samples indicated the enhancement of bulk resistivity and grain boundary resistivity with substitution. Saturation magnetizations of the substituted samples decreased and were ascribed to the replacement of Fe ions by Co-Ti ions at different crystallographic sites. The observed reduction in anisotropy constant indicated the disturbance in the magnetic axis. The multiferroic nature of the substituted samples at room temperature was confirmed from the soft ferroelectric loops. Room temperature magnetoelectric coupling coefficient was found to be largely enhanced with substitution, achieving an exceptionally high value of 182mV/cmOe for the x = 1.5 sample. This may prove useful for potential use in emerging device applications as a single phase room temperature multiferroic material.