Molecular solid glasses: new insights into frustrated systems

High sensitivity dielectric constant and heat capacity measurements are rep orted for solid N-2-Ar mixtures as well as pure N-2 in the presence of a sm all external ac electric field in the audio frequency range. Unexpected fie ld-induced aging and memory effects are observed for thermal cycles of fiel d cooled samples, above a well-defined temperature T-h. The magnitude and t emperature dependences of the effects exclude any simple interpretation in terms of lattice defects. The results show that the free energy surface inc ludes a complexity that allows for metastable states and that tunnelling ca n occur between the states.