Observation of lattice distortion in the low-dimensional quantum spin   system TiOBr by synchrotron x-ray diffraction
  We report here on physical properties and lattice distortion in the new quasi-one-dimensional spin system TiOBr by x-ray diffraction experiment using synchrotoron radiation. Comparing the crystal structure between TiOBr and TiOCl, the difference of b-axis length plays a key role for physical properties in both systems. By using single crystal of TiOBr, superlattice reflections were observed at (0 1.5 0) and (0 2.5 0). The temperature dependence of superlattice reflections imply the first order transition at $T_{c1}$=27K. We analyzed the data using the simple dimerization model. 
Tomoyuki Sasaki, Masaichiro Mizumaki, Kenichi Kato, Yasuo Watabe,   Yoshiki Nishihata, Masaki Takata and Jun Akimitsu