Münster 1997 – scientific programme

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TT: Tiefe Temperaturen

TT 10: Niederdimensionale Systeme, Lokalisierung

TT 10.5: Talk

Tuesday, March 18, 1997, 15:30–15:45, F1

In-chain and off-chain substitution study of the spin-Peierls compound CuGeO₃ — •M. Fischer¹, P. Lemmens¹, G. Güntherodt¹, M. Weiden², W. Richter², C. Geibel², and F. Steglich² — ¹2.Physikalisches Institut, RWTH Aachen, 52056 Aachen, Germany — ²FB Technische Physik, TH Darmstadt, 64289 Darmstadt, Germany

In-chain and off-chain substitutions were investigated in single crystalline samples of Cu_1−xZn_xGeO₃ and CuGe_1−xSi_xO₃, respectively, by means of Raman scattering. In CuGeO₃ a broad frustration-induced spinon continuum between 100 and 500 cm⁻¹ is observed above the spin-Peierls transition which is suppressed below T_SP and transferred into a growing 3D two-magnon density of states with its cut-off near 226 cm⁻¹ and a 1D gap-induced mode at 30 cm⁻¹. In substituted samples a suppression of the 1D gap-induced mode as well as a constant intensity of the spinon continuum are observed. In Si-substituted samples an overall reduction of the continuum intensity is observed. The two-magnon density of states as well as the x=0 spin-Peierls induced phonon at 370 cm⁻¹ gradually extend to higher T up to 60 K. These effects are attributed to an enhanced spin-spin correlation and a dimensional crossover at T_cross which is shifted to higher T in substituted samples.
Work supported by DFG through SFB 341 and BMBF FKZ 13N6586