Dresden 2009 – scientific programme
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MA: Fachverband Magnetismus
MA 18: Spin Structures and Magnetic Phase Transitions
MA 18.2: Talk
Wednesday, March 25, 2009, 10:30–10:45, HSZ 401
Spin-phonon coupling in CuCrS2 probed by inelastic neutron scattering — •Julia C.E. Rasch1,2, Martin Böhm1, Jürg Schefer2, Hannu Mutka1, Galina M. Abramova3, and Inga G. Vasilyeva4 — 1Institut Laue-Langevin, 6 rue Jules Horowitz, BP 156, 38042 Grenoble, Cedex 9, France — 2Laboratory for Neutron Scattering, ETH Zurich & Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland — 3L.V. Kirensky Institute of Physics SB RAS, Krasnoyarsk 660036, Russia — 4Nikolaev Institute of Inorganic Chemistry SB RAS, Novosibirsk 630090, Russia
The triangular lattice Heisenberg antiferromagnet CuCrS2 (S=3/2) with a quasi two-dimensional layered structure shows a complex three-dimensional magnetic long range order at TN=37 K. The onset of the magnetic ordering is directly coupled to a lattice distortion from R3m to monoclinic Cm as seen from high resolution neutron powder diffraction data on D1A (ILL). Inelastic neutron powder time-of-flight experiments on IN4 (ILL) revealed below TN a strong non-dispersive mode localized in Q at about ℏω=12 meV which is characteristic for magnetic clusters. An enhanced scattering intensity at the spin wave-phonon crossing point at ℏω=8 meV is additionally observed. We assume that the monoclinic lattice distortion in CuCrS2 plays a key role in relieving geometrical frustration and is analog to a Spin-Peierls transition in one dimension. Below TN the nearest neighbor Cr distances change irregular which makes the formation of a valence bond solid [1] favorable and accounts well for the non-dispersive mode at 12 meV. [1] C. Jia and J. H. Han, Phys. Rev. B 73, 172411 (2006)