Magneto-elastic model for the spin-Peierls compound TiOCl

D. MASTROGIUSEPPE; A. DOBRY

ICCMP, Brasilia, Brasil.

Workshop; Workshop on the Heisenberg model: past, present and future; 2009

ICCMP

Based on a simplified model of Heisenberg spins coupled to two-dimensional phonons, we derived a mechanism for the uniform-incommensurate transition in the spin-Peierls compound TiOCl. We show that the linearity of the phononic dispersion near the zone boundary due to the frustrated geometry of the lattice is the essential property which allows for the transition to an incommensurate phase. Extending a previous work by some of us, we present a phase diagram based on the XY model which is obtained by a minimization of the free energy with respect to the lattice distortion at different temperatures. We also show that the spin-spin z-component correlations in the incommensurate phase are modulated.