| Autor: |
Garcia-Fernandez, M., Scagnoli, V., Staub, U., Mulders, A. M., Janousch, M., Bodenthin, Y., Meister, D., Patterson, B. D., Mirone, A., Tanaka, Y., Nakamura, T., Grenier, S., Huang, Y., Conder, K. |
| Rok vydání: |
2008 |
| Předmět: |
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| Druh dokumentu: |
Working Paper |
| DOI: |
10.1103/PhysRevB.78.054424 |
| Popis: |
We have performed non-resonant x-ray diffraction, resonant soft and hard x-ray magnetic diffraction, soft x-ray absorption and x-ray magnetic circular dichroism measurements to clarify the electronic and magnetic states of the Co3+ ions in GdBaCo2O5.5. Our data are consistent with a 3+ Py Co HS state at the pyramidal sites and a 3+ Oc Co LS state at the octahedral sites. The structural distortion, with a doubling of the a axis (2ap x 2ap x 2ap cell), shows alternating elongations and contractions of the pyramids and indicates that the metal-insulator transition is associated with orbital order in the t2g orbitals of the 3+ Py Co HS state. This distortion corresponds to an alternating ordering of xz and yz orbitals along the a and c axes for the 3+ Py Co . The orbital ordering and pyramidal distortion lead to deformation of the octahedra, but the 3+ Oc Co LS state does not allow an orbital order to occur for the 3+ Oc Co ions. The soft x-ray magnetic diffraction results indicate that the magnetic moments are aligned in the ab plane but are not parallel to the crystallographic a or b axes. The orbital order and the doubling of the magnetic unit cell along the c axis support a non-collinear magnetic structure. The x-ray magnetic circular dichroism data indicate that there is a large orbital magnetic contribution to the total ordered Co moment. |
| Databáze: |
arXiv |
| Externí odkaz: |
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