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MA: Magnetismus
MA 4: Kondo / Schwer-Fermionen / Quasi-Niedrigdimensionale Systeme (gemeinsam mit TT)
MA 4.1: Talk
Monday, March 24, 2003, 10:15–10:30, HSZ/405
Raman scattering study of S=1/2 2D HAF K2V3O8 — •K.-Y. Choi1, G. Güntherodt1, B.C. Sales2, S.E. Nagler2, and P. Lemmens1,3 — 12. Physikalisches Institut, RWTH Aachen — 2Oak Ridge National Laboratory, Tennesse 37831, USA — 3MPI for Solid State Research, Stuttgart
We present an inelastic light scattering study of the two-dimensional antiferromagnetic Heisenberg spin system (2D HAF) K2V3O8. This S=1/2 square lattice antiferromagnet is formed by a vanadium layer which consists of corner-sharing magnetic (S=1/2) VO5 square pyramids and nonmagnetic (S=0) VO4 tetrahedra with K ions separating the layers. This compound may be used as a model system to understand the effect of a low symmetry exchange path and depletion of the magnetic sites on the excitation spectrum of a 2D HAF. In Raman scattering we observe a broad double peak maximum in the (a’b’) geometry that is identified as two-magnon scattering. Furthermore similar symmetry-forbidden signals in (aa) and (a’b’) symmetries arise. These scattering intensities persist up to 5J (15 TN) with J=12.8 K (TN= 4 K) determined from previous neutron scattering and susceptibility experiments. We will discuss these effects in the context of interlayer coupling and a possible electronic soft mode arising due to a local distortion of the VO5 square pyramids. Work supported by DFG SPP1073