Generalized Fluctuation Dissipation and Thermal Hysteresis of Dielectric Susceptibility in Frustrated Molecular Orientational Glasses

The results of high precision measurements of the dielectric susceptibility ε(T ) of solid oxygen in the low temperature α and β phases that have highly frustrated orientational interactions, are compared with the results of earlier studies of the thermal behavior of ε(T ) in solid N2-Ar mixtures. In the latter case the combination of disorder and frustration results in orientational glass states and strong hysteresis effects are observed for thermal cycles. The onset of the hysteresis marks the boundaries between the glass states, the long range periodically ordered state and the disordered state. A similar behavior is observed for solid O2 without substitutional disorder. In the β-phase of solid O2 the magnetic moments form a frustrated helical structure which transits to a non-magnetically frustrated collinear anti-ferromagnet in the α-phase. The molecular orientations form a highly frustrated linear alignment in both phases. The behavior of the dielectric susceptibility which measures the response of orientational degrees of freedom is compared for these two solids using a generalized fluctuation dissipation approach developed by Cugliandolo and Kurchan.