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Abstract

We study equilibration and ordering in the classical dipolar kagome Ising antiferromagnet, which we show behaves as a disorder-free fragile spin glass. By identifying an appropriate order parameter, we demonstrate a transition to the ordered state proposed by Chioar et al. [Phys. Rev. B 93, 214410 (2016)] with a 12-site unit cell that breaks time-reversal and sublattice symmetries, and further provide evidence that the nature of the transition is first order. Upon approaching the transition, the spin dynamics slow dramatically. The system readily falls out of equilibrium, overshooting the transition and entering a supercooled liquid regime. Using extensive Monte Carlo simulations, we show that the system exhibits super-Arrhenius behavior above the ordering transition. The best fit to the relaxation time is of the Vogel-Fulcher form with a divergence at a finite “glass transition” temperature in the supercooled regime. Such behavior, characteristic of fragile glasses, is particularly remarkable as the model is free of quenched disorder, does not straightforwardly conform to the avoided criticality paradigm, and is simple and eminently realizable in engineered nanomagnetic arrays.