Heat capacity and metal-insulator transition in Ti4O7 single crystals'

Abstract

Heat-capacity and entropy changes at the metal-insulator transitions have been measured on Ti4O7 single crystals. The 130-K transition is related to a disordering of the Ti3+ and Ti4+ chains at the unit cell level. Ti3+ pairing occurs in this phase but without any long-range order of the bonds. It is shown from both magnetic-susceptibility and specific-heat data that for the 150-K transition, the electronic contribution seems to be of the same order of magnitude as the lattice contribution.