International Workshop on Electronic Crystals
ECRYS-99

J. Phys. IV France 09 (1999) Pr10-279-Pr10-280
DOI: 10.1051/jp4:19991073

Spin gap state in α'-NaV₂O₅ studied by far infrared spectroscopy

D. Smirnov^{1, 2}, J. Leotin¹, O. Drachenko¹, P. Millet³, J. Jegoudez⁴ and A. Revcolevschi<sup>4

1</sup>  Laboratoire de Physique de la Matière Condensée, INSA-SNCMP, avenue de Rangueil, 31077 Toulouse, France
²  A.F. Ioffe Physical Technical Institute, 194021 St. Petersburg, Russia
³  Centre d'Élaboration de Matériaux et d'Études Structurales, 29 rue Jeanne Marvig, 31055 Toulouse, France
⁴  Laboratoire de Chimie des Solides, Université Paris-Sud, bâtiment 414, 91405 Orsay, France

Abstract
We present far infrared transmission measurements of α'-NaV₂O₅ single crystals. This material is known to undergo a spin-Peierls like transition at T_SP=35K. Below the transition temperature we observed together with expected new sharp phonon lines a strong gap-like depression of absorption occurring in the low energy part of a continuum likely connected with two-magnon excitations. The optical gap temperature dependence and its value closely match the spin gap values measured by neutron scattering experiments. Taking the optical gap as a fingerprint of the spin gap, we found that the relationship between the spin gap value and the dimerisation lattice parameter do not follow the scaling relation expected for the SP systems.

© EDP Sciences 1999