Regensburg 2002 – wissenschaftliches Programm

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MA: Magnetismus

MA 10: Poster : Dünne Schichten(1-21),Spinabh.Transp.(22-39),Exch.Bias(40-51),Spindyn.(52-55),Mikromag.(56-66),Partikel(67-74),Abb.Verf.(75-77),Oberfl.+Spinelektr.+Elektr.Theo+Mikromag(75-87),PÜ+Aniso+Werkst/Leg.(88-103),Mol.Mag.+N-dim+Messm.+Postdead(104-111

MA 10.106: Poster

Dienstag, 12. März 2002, 15:00–19:00, Bereich A

Exotic phononic and magnetic excitations in the zigzag chain KCuCl₃ and TlCuCl₃ — •K.-Y. Choi¹, P. Lemmens^1,2, G. Günderodt¹, A. Oosawa³, and H. Tanaka³ — ¹2. Phys. Inst., RWTH Aachen, 52056 Aachen, Germany — ²IMNF, TU Braunschweig, D-38106 Braunschweig, Germany — ³Dept. of Physics, Tokyo Institute of Technology, Oh-okayama, Meguro-ku, Tokyo 152-8551, Japan

Inelastic light scattering of the spin dimer chain systems KCuCl₃ and TlCuCl₃ with a substantial three-dimensional coupling exhibits exotic magnetic and phononic excitations. In both systems a broad maximum in scattering intensity is ascribed to a two-magnon continuum. The rather symmetric line shape is indicative of a strong interdimer interaction. The evolution of the spectrum with temperature exhibits an unusual behavior; with increasing temperature the spectral weight and peak position shift to higher energy. This may be attributed to a strong damping of two-magnon states at the lower continuum edge. No hint for the presence of magnon bound states has been found below 2Δ=40 cm⁻¹ (10.5 cm⁻¹) for KCuCl₃ (TlCuCl₃). In addition, a variety of interesting phenomena like unusual phonon anomalies in a large energy range and pronounced two-phonon scattering with chain polarization are reported. We suggest that this is due to strong spin-phonon coupling which is additionally evidenced by an asymmetric Fano line shape of phonons on the magnetic continuum.
We acknowledge support by DFG SPP1073.