A pressure and temperature dependent Raman study of the vibrational and spin dynamics in CuGeO3 is presented. A new low temperature, high pressure phase has been identified, and a pressure-temperature phase-diagram is proposed for CuGeO3. The pressure dependence of the effective exchange interaction, of the spin-Peierls gap, and of the spin-Peierls temperature strongly supports a model in which next nearest neighbor interactions stabilise the SP ground state. The Raman data allow for a quantitative estimate of the pressure dependence of the next nearest neighbor interactions.
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