J. Phys. IV France 12 (2002) Pr9-355
Optical properties of complex oxides: Vanadate ladders and related inorganic nanotubesJ.L. Musfeldt1, A.B. Sushkov1, J. Jegoudez2, A. Revcolevschi2, P. Millet3 and J. Galy3
1 University of Tennessee, U.S.A.
2 Université Paris-Sud, 91405 Orsay, France
3 CNRS Toulouse, France
Optical spectroscopy is a sensitive probe of charge, spin, and lattice degrees of freedom. In this talk, I will detail our magneto-optical work on alpha'-NaV2O5, a prototypical ladder material, as well as the new Na2V3O7 nanotubes. Using changes in electronic structure with temperature and applied magnetic field, we have mapped out the H-T phase diagram of alpha'-NaV2O5. We find a temperature independent phase boundary at 27 T which persists above Tc (34 K), a kink in Tc(H) near 27 T, and H 2 behavior of Tc(H) in the high field phase with an unusually small coupling constant. The energy scale of Tc and the newly discovered phase boundary at Hc (27 T) are identical. Confinement effects are investigated in the related nanotubes. Results include a larger gap than in analogous bulk materials as well as a low-energy rattling mode, which corresponds to the motion of Na+ ions inside the nanotube.
© EDP Sciences 2002