Dresden 2006 – wissenschaftliches Programm
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MA: Magnetismus
MA 5: Spin-Structures and Magnetic Phase Transitions I
MA 5.7: Vortrag
Montag, 27. März 2006, 11:45–12:00, HSZ 403
Orbital polarization and the metal-insulator transition in Ti2O3 — •Chun-Fu Chang1, Holger Ott1, Zhiwei Hu1, Maurits W. Haverkort1, Hua Wu1, H. H. Hsieh2, H. -J Lin3, C. T. Chen3, and Liu Hao Tjeng1 — 1II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany — 2Chung Cheng Institute of Technology, National Defense University, Taoyuan 335, Taiwan — 3National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu 30076, Taiwan
Ti2O3 undergoes a broad metal-insulator transition (MIT) at around 400-600 K without a change in the symmetry of the corundum structure. There is a long-standing debate about the mechanism of this unusual MIT. We have set out to do polarization-dependent x-ray absorption spectroscopy measurements and cluster calculations using the configuration interaction model. We have found that the dimer effect of the vertical Ti-Ti pairs play a crucial role in the MIT. Our results point out that a gradual change of the orbital occupation of the Ti 3d states accompanies this abnormally broad transition. This orbital redistribution assists the MIT in a manner that the intersite exchange interaction of Ti-Ti pair is reduced and the effective in-plane band widths of the Ti 3d states are increased.