Molecular solid glasses: New insights into frustrated systems

Abstract

High sensitivity dielectric constant and heat capacity measurements are reported for solid N2-Ar mixtures as well as pure N2 in the presence of a small external ac electric field in the audio frequency range. Unexpected fieldinduced aging and memory effects are observed for thermal cycles of field cooled samples, above a well-defined temperature Th. The magnitude and temperature dependences of the effects exclude any simple interpretation in terms of lattice defects. The results show that the free energy surface includes a complexity that allows for metastable states and that tunnelling can occur between the states.