@article{SisLab1796,
          volume = {117},
           title = {Local geometric and electronic structures and origin of magnetism in Co-doped BaTiO3 multiferroics},
          author = {The Long Phan and Duc Thang Pham and A. Ho T. and V. Manh T. and Dang Thanh Tran and D. Lam V and T. Dang N. and C. Yu S.},
            year = {2015},
         journal = {Journal Applied Physics},
             url = {https://eprints.uet.vnu.edu.vn/eprints/id/eprint/1796/},
        abstract = {We have prepared polycrystalline samples BaTi1?xCoxO3 (x = 0?0.1) by solid-state reaction. X-ray diffraction and Raman-scattering studies reveal the phase separation in crystal structure as changing Co-doping content (x). The samples with x = 0?0.01 are single phase in a tetragonal structure. At higher doping contents (x {\ensuremath{>}} 0.01), there is the formation and development of a secondary hexagonal phase. Magnetization measurements at room temperature indicate a coexistence of paramagnetic and weak-ferromagnetic behaviors in BaTi1?xCoxO3 samples with x {\ensuremath{>}} 0, while pure BaTiO3 is diamagnetic. Both these properties increase with increasing x. Analyses of X-ray absorption spectra recorded from BaTi1?xCoxO3 for the Co and Ti K-edges indicate the presence of Co2+ and Co3+ ions. They locate in the Ti4+ site of the tetragonal and hexagonal BaTiO3 structures. Particularly, there is a shift of oxidation state from Co2+ to Co3+ when Co-doping content increases. We believe that the paramagnetic nature in BaTi1?xCoxO3 samples is due to isolated Co2+ and Co3+ centers. The addition of Co3+ ions enhances the paramagnetic behavior. Meanwhile, the origin of ferromagnetism is due to lattice defects, which is less influenced by the changes caused by the variation in concentration of Co2+ and Co3+ ions.
The-Long , P. D. Thang2, T. A. 1, T. V. Manh1, Tran Dang Thanh1,3, V. D. Lam3, N. T. Dang4 and S. C. Yu}
}