Aging and memory properties of topologically frustrated magnets

The model 2d kagomé system (H3O)Fe3(SO4)2(OH)6 and the 3d pyrochlore Y2Mo2O7 are two well characterized examples of low-disordered frustrated antiferromagnets which rather than condensing into spin liquid have been found to undergo a freezing transition with spin glass-like properties. We explore more deeply the comparison of their properties with those of spin glasses, by the study of characteristic rejuvenation and memory effects in the nonstationary susceptibility. While the pyrochlore shows clear evidence for these nontrivial effects, implying temperature selective aging, that is characteristic of a wide hierarchical distribution of equilibration processes, the kagomé system does not clearly show these effects. Rather, it seems to evolve towards the same final state independently of temperature.