Berlin 2008 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 32: Postersession II: Spinstruct./Phase Trans. (1-10); Spinelectronics (11-15); Thin Films (16 - 36); Particles/Clusters (37-45); Multiferroics (46-54); Spindynamics/Spin Torque (55 - 76); Post Deadlines (77-79)
MA 32.3: Poster
Freitag, 29. Februar 2008, 11:15–14:00, Poster E
Spin-strain coupling in NiCl2-4SC(NH2)2 — •O. Chiatti1, A. Sytcheva1, J. Wosnitza1, S. Zherlitsyn1, V. S. Zapf2, M. Jaime2, and A. Paduan-Filho3 — 1Forschungszentrum Dresden-Rossendorf, Hochfeld-Magnetlabor Dresden (HLD), 01314 Dresden, Germany — 2National High Magnetic Field Laboratory, Los Alamos National Lab, Los Alamos, NM — 3Instituto de Fisica, Universidade de São Paulo, Brazil
We report results of sound-velocity and sound-attenuation measurements in the quantum S = 1 spin-chain magnet NiCl2-4SC(NH2)2, in magnetic fields up to 18 T. This material is discussed in the context of Bose-Einstein condensation of magnons. The longitudinal c33 acoustic mode, which has a propagation direction along the spin chains, shows pronounced spin-lattice effects. This mode demonstrates a softening in the vicinity of the field-induced antiferromagnetic ordering (below T = 1.2 K), accompanied by an energy dissipation in the acoustic wave. A broad maximum has been observed in the temperature dependence of the sound velocity at 44 K. The low-temperature sound-velocity and sound-attenuation behavior is subject to fluctuations of Ni spin degrees of freedom resulting in frequency-dependent effects. The B−T phase diagram obtained from the ultrasonic measurements is compared with results extracted from other experimental investigations. The ultrasonic results are analyzed with a theory based on exchange-striction spin-phonon coupling.