Magnetic properties of (BEDT-TTF)(ClMeTCNQ) studied by ESR under pressure: a neutral-ionic crossover and thermoinduced mesophase.

ABSTRACT

The neutral-ionic (NI) phase transition in (BEDT-TTF)(ClMeTCNQ) is studied with ESR under pressure to tune the transition temperature. Broad peak structures observed in the spin susceptibility around T(NI) are analyzed with the assumption of a spin-Peierls gap of 1100 K, which demonstrates the continuous evolution of ionic domain fraction through T(NI) over the extent T(W) proportional, variantT(NI). An unexpected feature is the presence of sizable ionic droplets even at T>>T(NI), which is ascribed to the tiny energy difference between the two phases.