TUNABILITY OF CROSSOVER PHASES IN MX-COMPOUNDS

MX materials offer the unique opportunity to study a whole variety of phases from CDW phases over long-range mixed phases to SDW phases by c hanging the chemical composition, or by applying external pressure. Es pecially in the regime of the mixed, long wavelength phases, where the free energy differences are small, a magnetic field can be used to se lect a specific phase characterized by certain charge and spin correla tions. We discuss the characteristics of those phases and their releva nt parameters regimes and experimental signatures. Since the free ener gy differences between various phases are small we also discuss the in fluence of non-adiabaticity and disorder on their relative stability.