Abstract
We present a parametric study of the diffuse magnetic scattering at positions in reciprocal space, ascribed to a frozen antiferromagnetic spin ice state in single-crystalline . Our high-resolution neutron scattering measurements show that the elastic meV meV) scattering develops strongly below 275 mK, and correlates with the opening of a spin gap of to 0.08 meV over most of the Brillouin zone. The nature of the transition at 275 mK has many characteristics of spin glass behavior, consistent with ac-susceptibility measurements. The application of a magnetic field of 0.075 T applied along the direction destroys the elastic scattering, revealing the fragility of this short-range ordered ground state. We construct a refined - phase diagram for and fields which incorporates this frozen spin ice regime and the antiferromagnetic long-range order previously known to be induced in relatively large fields. Specific heat measurements on the same crystal reveal a sharp anomaly at 450 mK and no indication of a transition near 275 mK. We conclude that the higher temperature specific heat peak is not related to the magnetic ordering but is likely a signal of other, nonmagnetic dipole correlations.
- Received 29 November 2013
- Revised 20 June 2014
DOI:https://doi.org/10.1103/PhysRevB.90.014429
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