We study the ferromagnetic phase transition in a randomly layered Heisenberg magnet using large-scale Monte Carlo simulations. Our results provide numerical evidence for the infinite-randomness scenario recently predicted within a strong-disorder renormalization-group approach. Specifically, we investigate the finite-size scaling behavior of the magnetic susceptibility, which is characterized by a nonuniversal power-law divergence in the Griffiths phase. We also study the perpendicular and parallel spin-wave stiffnesses in the Griffiths phase. In agreement with the theoretical predictions, the parallel stiffness is nonzero for all temperatures T < Tc. In contrast, the perpendicular stiffness remains zero in part of the ordered phase, giving rise to anomalous elasticity. In addition, we calculate the in-plane correlation length, which diverges already inside the disordered phase at a temperature significantly higher than Tc. The time autocorrelation function within model A dynamics displays an ultraslow logarithmic decay at criticality and a nonuniversal power law in the Griffiths phase.



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© 2011 American Physical Society (APS), All rights reserved.

Publication Date

01 Nov 2011

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