X-ray scattering study of the spin-Peierls transition and soft phonon behavior in TiOCl

Journal Article · Sat Dec 01 04:00:00 EST 2007 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PHYSREVB.76.214304· OSTI ID:21052804

Abel, E T; Matan, K; Moncton, D E; Lee, Y S ^[1]; Chou, F C ^[2]; Isaacs, E D ^[3]; Sinn, H; Alatas, A ^[4]

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1. Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)
2. Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan (China)
3. Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439 (United States)
4. Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

We have studied the S=1/2 quasi-one-dimensional antiferromagnet TiOCl using single crystal x-ray diffraction and inelastic x-ray scattering techniques. The Ti ions form staggered spin chains which dimerize below T{sub c1}=66 K and have an incommensurate lattice distortion between T{sub c1} and T{sub c2}=92 K. Based on our measurements of the intensities, wave vectors, and harmonics of the incommensurate superlattice peaks, we construct a model for the incommensurate modulation. The results are in good agreement with a soliton lattice model, though some quantitative discrepancies exist near T{sub c2}. The behavior of the phonons has been studied using inelastic x-ray scattering with {approx}2 meV energy resolution. For the first time, a zone-boundary phonon which softens at the spin-Peierls temperature T{sub SP} has been observed. Our results show reasonably good quantitative agreement with the Cross-Fisher [Phys. Rev. B. 19, 402 (1979)] theory for the phonon dynamics at wave vectors near the zone boundary and temperatures near T{sub SP}. However, not all aspects of the data can be described, such as the strong overdamping of the soft mode above T{sub SP}. Overall, our results show that TiOCl is a good realization of a spin-Peierls system, where the phonon softening allows us to identify the transition temperature as T{sub SP}=T{sub c2}=92 K.

• OSTI ID: 21052804
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Journal Name: Physical Review. B, Condensed Matter and Materials Physics Journal Issue: 21 Vol. 76; ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ENERGY RESOLUTION
HARMONICS
MEV RANGE
MONOCRYSTALS
ONE-DIMENSIONAL CALCULATIONS
PHONONS
SOLITONS
SPIN
SUPERLATTICES
TITANIUM COMPOUNDS
TITANIUM IONS
TRANSITION TEMPERATURE
VECTORS
X-RAY DIFFRACTION