Order by Disorder and Energetic Selection of the Ground State in the XY Pyrochlore Antiferromagnet Er2Ti2O7. An Inelastic Neutron Scattering Study

Sylvain Petit (1) , Julien Robert (1) , Solene Guitteny (1) , Pierre Bonville (2) , Claudia Decorse (3) , Jacques Ollivier (4) , Hannu Mutka (4) , Michel J P Gingras (5, 6) , Isabelle Mirebeau (1)

1 LLB - UMR 12 - Laboratoire Léon Brillouin
2 LNO - Laboratoire Nano-Magnétisme et Oxydes
3 CHIMSOL - Laboratoire de Physico-Chimie de l'Etat Solide
4 ILL - Institut Laue-Langevin
5 Perimeter Institute for Theoretical Physics [Waterloo]
6 University of Waterloo [Waterloo]

Examples of materials where an " order by disorder " mechanism is at play to select a particular ground state are scarce. It has recently been proposed, however, that the antiferromagnetic XY pyrochlore Er 2 Ti 2 O 7 reveals a most convincing case of this mechanism, with the observation of a spin gap at zone centers having recently been interpreted as a corroboration of this physics. Here we argue, however, that the anisotropy generated by the interaction-induced admixing between the crystal-field ground and excited levels provides for an alternative mechanism. It especially predicts the opening of a spin gap of about 15 μeV, which is of the same order of magnitude as the one observed experimentally. We report high-resolution inelastic neutron scattering data which can be well understood within this scenario.

Domains: Physics [physics]

Sylvain Petit, Julien Robert, Solene Guitteny, Pierre Bonville, Claudia Decorse, et al.. Order by Disorder and Energetic Selection of the Ground State in the XY Pyrochlore Antiferromagnet Er2Ti2O7. An Inelastic Neutron Scattering Study. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2014, 90, pp.60410. ⟨10.1103/PhysRevB.90.060410⟩. ⟨cea-01377031⟩