Abstract
On the basis of single-crystal x-ray diffraction we show that TiPO undergoes a spin-Peierls distortion below 74.5(5) K, with a dimerization of the Ti chains along the axis. Between 74.5(5) and 111.6(3) K, TiPO develops an incommensurate (IC) phase with temperature-dependent vector (,0,0). Density functional calculations strongly suggest that the IC phase results from a frustration of the lock-in spin-Peierls transition due to the competition of three energetically almost degenerate crystal structures and elastic coupling of the Ti chains via the bridging PO units. The phase transition into the IC phase is of second order, but the lock-in transition into the spin-Peierls distortion below 74.5 K is of weak first order in nature.
- Received 20 July 2013
DOI:https://doi.org/10.1103/PhysRevB.88.184420
©2013 American Physical Society