Structural dielectric and magnetic properties of Gd and Ti co-doped BiFeO3 multiferroics at room temperature

Abstract

Structural, dielectric and magnetic properties of BiFeO3 multiferroic samples, co-doped with magnetic Gd and non-magnetic Ti in place of Bi and Fe, respectively, were reported at room temperature. The nominal compositions of Bi0.9Gd0.1Fe1-xTixO3 (x = 0.00 - 0.25) ceramics were synthesized by conventional solid state reaction technique. X-ray diffraction patterns revealed that the substitution of Fe by Ti induces a phase transition from rhombohedral to orthorhombic at x > 0.20. Morphological studies demonstrated that the average grain size was reduced from ~1.5 μm to ~200 nm with the increase in Ti content. Due to Ti substitution, the dielectric constant was stable over a wide range of high frequencies (30 kHz to 20 MHz) by suppressing the dispersion at low frequencies. The dielectric properties of the compounds are associated with their improved morphologies and reduced leakage current densities probably due to the lower concentration of oxygen vacancies in the compositions. Magnetic properties of Bi0.9Gd0.1Fe1-xTixO3 (x = 0.00 - 0.25) ceramics measured at room temperature were enhanced with Ti substitution up to 20% compared to that of pure BiFeO3 and Ti undoped Bi0.9Gd0.1FeO3 samples. The enhanced magnetic properties might be attributed to the substitution induced suppression of spiral spin structure of BiFeO3. An asymmetric shift both in the field and magnetization axes of magnetization versus magnetic field curves was observed. This indicates the presence of exchange bias effect in these compounds notably at room temperature.