P. Millet — Page 2 | Searcharxiv

arXiv1998

Study of spin-Peierls transition in alpha'--NaV2O5 by infrared reflectivity

Polarized infrared reflectivity measurements have been performed on single crystals of the spin-Peierls compound alpha'-NaV2O5 in the temperature range 20-300 K. Pronounced spectral features associated with the formation of the dimerized phase were detected both in the a- and b-polarizations (perpendicular and parallel to the spin-1/2 chains, respectively). The temperature dependence of a salient spectral line at 718 cm^-1 sharply rising below the transition temperature T_SP obeys a (1-T/T_SP)^(2beta) law with T_SP \simeq 34.3$K and beta \simeq 0.25. In addition, a continuum signal is observed in the whole temperature range in the a-polarized optical conductivity spectra. In order to interpret these results, calculations of the static dimerization and of the optical conductivity based on a mean-field and a dynamical treatment of the lattice respectively are proposed.

cond-mat.str-el↗

arXiv1998

Magnetic properties of the coupled ladder system MgV$_2$O$_5$

We present magnetic susceptibility measurements on MgV$_2$O$_5$, a compound in which the vanadium oxide planes have the same topology as in CaV$_2$O$_5$. The most striking property is that there is an energy gap of about 15 K, much smaller than in CaV$_2$O$_5$, where the values reported are of the order of 500 K. We show that this may be understood naturally in terms of the phase diagram of the frustrated, coupled ladder system. This analysis leads to the prediction that MgV$_2$O$_5$ should have incommensurate dynamic spin fluctuations.

cond-mat.str-el↗