Electronic and atomic structures of YMnO3 and YMn2/3Tm1/3O3 (Tm= Co, Ni and Cu)
| Autor: | Yu-Shin Chen, 陳昱昕 |
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| Rok vydání: | 2009 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 97 X-ray absorption spectroscopy measurements have been performed to elucidate local electronic and atomic structures of 3d-transition metal doped yttrium manganites (YMnO3) with chemical formula YMn2/3Tm1/3O3 (Tm= Co, Ni and Cu). The Mn L3-edge and K-edge XANES results indicate the direct substitution of Tm2+ for Mn3+, so that the positive effective charge of Mn ions are increased. Tm-doping is also found to induce substantial broadening of the Mn L3-edge feature, which suggests enhancement of the delocalization of Mn 3d eg subbands and conductivity. Local spin density approximation (LDA) + U (Hubbard U parameter) calculation shows that the leading features in the Mn L3-edge XANES spectra of YMn2/3Tm1/3O3 are due to majority-spin Mn eg subband rather than the Mn t2g subband commonly assigned. The comparison between O K-edge XANES spectrum of YMn2/3Ni1/3O3 and the LDA+U calculation shows significant contribution of O 2p and minority-spin Ni 3d eg hybridized states to the second feature of the O K-edge XANES spectra. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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