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journal id: "physicalxreviewxb"
| Authors | M. García-Fernández, V. Scagnoli, U. Staub, A.M. Mulders, M. Janousch, Y. Bodenthin, D. Meister, B.D. Patterson, A. Mirone, Y. Tanaka, T. Nakamura, S. Grenier, Y. Huang, K. Conder | | Title | Magnetic and electronic Co states in the layered cobaltate GdBaCo2O5.5−x |
| Journal | Physical Review B |
| Volume | 78 |
| Year | 2008 |
| Issue | 5 |
| Pages | 054424- |
| ISSN | 10980121 |
| Faculty | Faculty of Science |
| Institute/dept. | FNWI: Van der Waals-Zeeman Institute (WZI) |
| Abstract | We have performed nonresonant 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 high-spin (HS) state at the states of the Co3+, ions in GdBaCo2O5.5. Our data are consistent with a Co-Py(3+) pyramidal sites and a Co-Oc(3+), low-spin (LS) state at the octahedral sites. The structural distortion with a doubling of the a axis (2a(p)X2a(p)X2a(p) cell) shows alternating elongations and contractions of the pyramids, and indicates that the metal-insulator transition is associated with orbital order in the t(2g) orbitals of the Co-Py(3+) HS state. This distortion corresponds to an alternating ordering of xz and yz orbitals along the a and c axes for the Co-Py(3+). The orbital ordering and pyramidal distortion lead to deformation of the octahedra but the Co-Oc(3+) LS state does not allow an orbital order to occur for the Co-Oc(3+), 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 noncollinear magnetic structure. The x-ray magnetic circular dichroism data indicate that there is a large orbital magnetic contribution to the total ordered Co moment. |
| Document type | Article |
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