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AM: Magnetismus
AM 6: Magnetische Phasenübergänge in drei- und niederdimensionalen Strukturen
AM 6.1: Talk
Monday, March 17, 1997, 17:15–17:30, F4
Magnetic interactions and the pressure-temperature phase diagram of CuGeO3. — •Paul H. M. van Loosdrecht1,2, J. Zeman1, G. Martinez1, G. Dhalenne3, and A. Revcolevschi3 — 1MPI/CNRS Hochfeld Magnet Labor, 25 Avenue des Martyrs, F 38042 Grenoble Cedex 9, Frankreich — 22. Physikalisches Institut der RWTH-Aachen, Templergraben 55, 52056 Aachen — 3Lab. de Chimie des Solides, Univ. Paris-Sud, F-914052 Orsay, Frankreich
CuGeO3 appears to be a good example of a magneto-elastic one-dimensional isotropic S=1/2 Heisenberg antiferromagnet which undergoes a spin-Peierls (SP) transition at low temperature. Several experimental results show however that this may not be the case. In particular recent reports have indicated that next nearest neighbor (nnn) interactions may play an important role, both in the properties of the uniform high temperature phase as well as in driving the SP transition itself.
Using pressure dependent Raman spectroscopy we have studied the pressure-temperature phase diagram of CuGeO3, in particular in respect to the magnetic properties[1]. The data are found to be in good agreement with a simple nnn model, and allow for an evaluation of the nnn interaction strength as a function of pressure. The relative weak influence of magneto-elastic interactions on the SP transition is further exemplified by the observation of a structural phase transition at high pressure which does not influence the SP transition itself.
[1] P.H.M. van Loosdrecht et al., submitted to Phys. Rev. Lett.