Incommensurate to commensurate phase transition in a new spin-Peierls system TiOBr

We report here on the observation of superlattice reflections in the new quasi-one-dimensional spin system TiOBr by electron and synchrotron radiation X-ray diffractions. We discussed on crystal symmetry and temperature dependence of superlattice reflections. Superlattice reflections can be observed at (h, k + 1/2, 0) below T-cl and (h +/- delta(h), k +/- delta k, 0) above Tcl; (h + k = 2n). We discussed the origin of two phase transitions, T-cl(= 27K) and T-c2(= 47K) in TiOBr. (c) 2006 Elsevier B.V. All rights reserved.