Ferroelectric and ferromagnetic properties of Gd-modified BiFeO3

The polycrystalline samples of gadolinium (Gd)-modified bismuth iron oxide, Bi1−xGdxFeO3 (BGFO) with x=0, 0.05, 0.15, 0.25 were prepared by a standard high-temperature solid-state reaction technique. A preliminary X-ray structural analysis was carried out to examine the structural deformation and stability of Gd-modified BiFeO3. Room temperature surface morphology and textures of the samples were recorded by a scanning electron microscope, which reveal the uniform distribution of the plate-and rod-shaped grains in the samples. The grain size decreases with increase of Gd content in BGFO. Studies of dielectric and electric properties in a wide range of frequency (1 kHz-1 MHz) and temperature (30-400 °C) using complex impedance spectroscopic method have provided many new results. With higher Gd-concentration, dielectric constant and tangent loss of BGFO increases and decreases respectively at room temperature. Generally, the spontaneous and remnant polarizations are found to be enhanced on Gd substitutions in BFO. Studies of temperature dependence of electrical conductivity exhibit that all the samples follow Arrhenius-type of electrical conductivities behavior. The frequency dependence of ac conductivity suggests that the samples obey Jonscher's universal power law. The magneto-electric coupling coefficient of BFO is enhanced on increasing Gd content in BGFO.