Evidence for Spin Glass Transition in Hexagonal DyMnO3 without Substitutional Disorder

Abstract

The magnetic interactions in the multiferroic hexagonal (h-) REMnO3 with magnetic RE3+ ions are geometrically frustrated, but only long-range ordering transitions have been reported so far. Using dc and ac susceptibility measurements on well-characterized single crystals of h-DyMnO3, we present here evidence for a spin glass (SG) transition around the spin-reordering transition at TDy ≈ 7 K. This transition is shown to exhibit history-dependent irreversibility, de Almeida-Thouless line in the T-H plane, and critical slowing down of spin dynamics as per Vogel-Fulcher and power law. We have also confirmed that the SG phase exhibits nonexponential decay of thermoremanent magnetization, as well as memory and rejuvenation effects. The SG phase of h-DyMnO3 is unconventional as it occurs without any apparent disorder, like in other geometrically frustrated systems, but bears perfect phenomenological similarities with the SG phases in disordered systems. Using low-temperature X-ray diffraction studies, we also present experimental evidence for magnetoelastic coupling, which we believe is the source of randomness required for SG transition in the geometrically frustrated h-DyMnO3 in the absence of any substitutional disorder. Copyright © 2019 American Chemical Society.