![]() | Only 14 pages are availabe for public view |
Abstract Pure BaTiO and CoFe O phases are prepared by sol-gel and autocombustion methods respectively. Two groups of double phase magnetoelectric composites with the molecular formula xCoFe :(1x)BaTiO and yBaTiO :(1-y)CoFe O (x and y are molecular weight ratios) are prepared by two step chemical method . The XRD patterns measured of all samples proves that both BaTiO and CoFe O phases with tetragonal perovskite and spinel cubic structures respectively are present. The analysis of XRD Patterns show that, all prepared samples have crystallite size in the nano scale, and the lattice parameters , crystallite size and strain change depending on the composition ratio. Also HRTEM micrographs for some selected samples show that the composites have particles with sizes in the nanoscale. Magnetic hysteresis loops measured for all composite samples with CoFe content show that, the samples have normal ferromagnetic behavior up to 500 K. Saturation and residual magnetization depends linearly on CoFe content. The relation between coercivity and particle size as well as field cooling zero field cooling (FC-ZFC) curves prove the existence of magnetic nanoparticles with single magnetic domain. The dielectric permittivity (e’) and dielectric loss (e’’) spectra measured for all samples depend on the composition ratio. When a magnetic field with different strength is applied during measurements , (e’ ) and (e’’)spectra are suppressed, the effect is represented by magnetocapacitance (MC). MC is found to be frequency and field dependent. After removing the external field, (e’ ) and (e’’)spectra have values lower that in the absence of field, this is attributed to irreversible direct reaction between magnetic field and electric dipoles. |