No abstract

We report the effect of nickel doping on the structural, optical, and magnetic properties of Bi 0.5 K 0.5 TiO 3 nanocrystal. The X-ray diffraction results indicated that Ni was substituted into the Ti sites in Bi 0.5 K 0.5 TiO 3 and the NiTiO 3 phase was formed when Ni concentration was higher than 3 mol%. The band gap value decreased from 3.31 eV to 2.96 eV when the Ni concentration changed from 0 to 3 mol% and then increased with higher Ni concentration. Both weak-ferromagnetism and diamagnetism coexisted in un-doped Bi 0.5 K 0.5 TiO 3 samples. The ferromagnetic signal strongly influenced the paramagnetic signal for Ni-doped Bi 0.5 K 0.5 TiO 3 samples at room temperature. The room-temperature ferromagnetism in Ni-doped Bi 0.5 K 0.5 TiO 3 samples could be contributed by intrinsic reason due to presence of Ni ion in Bi 0.5 K 0.5 TiO 3 crystal and by extrinsic reason due to segregation of NiTiO 3 clusters when Ni concentration was over 3 mol% threshold. This method may provide a useful way to get both single-phase multiferroics and composite multiferroics materials.

ermodynamic properties and anharmonic effects in X-ray absorption fine structure (XAFS) have been studied based on the anharmonic correlated Debye model Debye-Waller factors presented in terms of cumulant expansion. e derived analytical expressions of three first XAFS cumulants involve more information on phonon-phonon interactions taken from integration over the first Brillouin zone. Many-body effects are taken into account in the present one-dimensional model based on the first shell near neighbor contributions to the vibrations between absorber and backscatterer atoms. Morse potential is assumed to describe single-pair atomic interaction included in the derived anharmonic interatomic effective potential. e present theory can be applied to any crystal structure including complex systems. Numerical results for Cu and Ni are found to be in good agreement with experiment and with those of the other theories.

In this work, X-ray absorption fine structure (XAFS) of bcc crystals and it Fourier transformmagnitude have been studied based on the anharmonic correlated Debye model high-order expandedDebye-Waller factors. The many-body effects are taken into account in the present one-dimensionalmodel based on the anharmonic effective potential that includes interactions of absorber andbackscatterer atoms with their first shell near neighbors, where Morse potential is assumed to describethe single-pair atomic interaction. Analytical expressions of four first temperature-dependent cumulantsof bcc crystals have been derived using the many-body perturbation approach. The obtained cumulantsare applied to calculating XAFS spectra and their Fourier transform magnitudes. Numerical results forFe are found to be in good agreement with experiment.