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Title: Neutron spectroscopic study of crystalline electric field excitations in stoichiometric and lightly stuffed Yb2Ti2O7

Time-of-flight neutron spectroscopy has been used to determine the crystalline electric field Hamiltonian, eigenvalues and eigenvectors appropriate to the J=7/2 Yb3+ ion in the candidate quantum spin ice pyrochlore magnet Yb2Ti2O7. The precise ground state of this exotic, geometrically frustrated magnet is known to be sensitive to weak disorder associated with the growth of single crystals from the melt. Such materials display weak “stuffing,” wherein a small proportion, approximately 2%, of the nonmagnetic Ti4+ sites are occupied by excess Yb3+. We have carried out neutron spectroscopic measurements on a stoichiometric powder sample of Yb2Ti2O7, as well as a crushed single crystal with weak stuffing and an approximate composition of Yb2+xTi2–xO7+y with x = 0.046. All samples display three crystalline electric field transitions out of the ground state, and the ground state doublet itself is identified as primarily composed of mJ = ±1/2, as expected. However, stuffing at low temperatures in Yb2+xTi2–xO7+y induces a similar finite crystalline electric field lifetime as is induced in stoichiometric Yb2Ti2O7 by elevated temperature. In conclusion, an extended strain field exists about each local “stuffed” site, which produces a distribution of random crystalline electric field environments in the lightly stuffed Yb2+xTi2–xO7+y, in addition to producing amore » small fraction of Yb ions in defective environments with grossly different crystalline electric field eigenvalues and eigenvectors.« less
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [4] ;  [5]
  1. McMaster Univ., Hamilton, ON (Canada)
  2. Colorado State Univ., Fort Collins, CO (United States)
  3. Brockhouse Institute for Materials Research, Hamilton, ON (Canada)
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  5. McMaster Univ., Hamilton, ON (Canada); Brockhouse Institute for Materials Research, Hamilton, ON (Canada); Canadian Institute for Materials Research, Toronto, ON (Canada)
Publication Date:
OSTI Identifier:
1224753
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Physical Review. B, Condensed Matter and Materials Physics
Additional Journal Information:
Journal Volume: 92; Journal Issue: 13; Journal ID: ISSN 1098-0121
Publisher:
American Physical Society (APS)
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE