Gapless quantum excitations from an icelike splayed ferromagnetic ground state in stoichiometric ${\mathrm{Yb}}_2{\mathrm{Ti}}_2{\mathrm{O}}_7$

Journal Article · Tue Feb 02 23:00:00 EST 2016 · Physical Review B

DOI: https://doi.org/10.1103/PhysRevB.93.064406 · OSTI ID:1261510

Gaudet, J. ^[1]; Ross, K. A. ^[2]; Kermarrec, E. ^[1]; Butch, N. P. ^[3]; Ehlers, G. ^[4]; Dabkowska, H. A. ^[5]; Gaulin, B. D. ^[6]

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1. McMaster Univ., Hamilton, ON (Canada)
2. Johns Hopkins Univ., Baltimore, MD (United States); National Inst. of Standards and Technology, Gaithersburg, MD (United States)
3. National Inst. of Standards and Technology, Gaithersburg, MD (United States)
4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
5. Brockhouse Inst. for Materials Research, Hamilton, ON (Canada)
6. McMaster Univ., Hamilton, ON (Canada); Brockhouse Inst. for Materials Research, Hamilton, ON (Canada); Canadian Inst. for Materials Research, Toronto, ON (Canada)

We know the ground state of the quantum spin ice candidate magnet Yb₂Ti₂O₇ to be sensitive to weak disorder at the similar to 1% level which occurs in single crystals grown from the melt. Powders produced by solid state synthesis tend to be stoichiometric and display large and sharp heat capacity anomalies at relatively high temperatures, T-C similar to 0.26 K. We have carried out neutron elastic and inelastic measurements on well characterized and equilibrated stoichiometric powder samples of Yb₂Ti₂O₇ which show resolution-limited Bragg peaks to appear at low temperatures, but whose onset correlates with temperatures much higher than T-C. The corresponding magnetic structure is best described as an icelike splayed ferromagnet. In the spin dynamics of Yb₂Ti₂O₇ we see the gapless on an energy scale <0.09 meV at all temperatures and organized into a continuum of scattering with vestiges of highly overdamped ferromagnetic spin waves present. These excitations differ greatly from conventional spin waves predicted for Yb₂Ti₂O₇'s mean field ordered state, but appear robust to weak disorder as they are largely consistent with those displayed by nonstoichiometric crushed single crystals and single crystals, as well as by powder samples of Yb₂Ti₂O₇'s sister quantum magnet Yb₂Ti₂O₇.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 1261510
• Journal Information: Physical Review B, Journal Name: Physical Review B Journal Issue: 6 Vol. 93; ISSN 2469-9950; ISSN PRBMDO
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English