Suppression of the commensurate spin-Peierls state in Sc-doped TiOCl

TL;DR

This study investigates how non-magnetic Sc doping affects the spin-Peierls state in TiOCl, showing suppression of long-range order and changes in incommensurate fluctuations even at low doping levels.

Contribution

It demonstrates that minimal Sc doping disrupts the spin-Peierls state, preventing long-range order and altering incommensurate fluctuations in TiOCl.

Findings

Sc doping suppresses commensurate fluctuations

Incommensurate scattering persists without lock-in transition

Doping reduces lattice displacement size

Abstract

We have performed x-ray scattering measurements on single crystals of the doped spin-Peierls compound Ti(1-x)Sc(x)OCl (x = 0, 0.01, 0.03). These measurements reveal that the presence of non-magnetic dopants has a profound effect on the unconventional spin-Peierls behavior of this system, even at concentrations as low as 1%. Sc-doping suppresses commensurate fluctuations in the pseudogap and incommensurate spin-Peierls phases of TiOCl, and prevents the formation of a long-range ordered spin-Peierls state. Broad incommensurate scattering develops in the doped compounds near Tc2 ~ 93 K, and persists down to base temperature (~ 7 K) with no evidence of a lock-in transition. The width of the incommensurate dimerization peaks indicates short correlation lengths on the order of ~ 12 angstroms below Tc2. The intensity of the incommensurate scattering is significantly reduced at higher Sc concentrations, indicating that the size of the associated lattice displacement decreases rapidly as a function of doping.