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Title: Momentum-resolved observations of the phonon instability driving geometric improper ferroelectricity in yttrium manganite

Magnetoelectrics offer tantalizing opportunities for devices coupling ferroelectricity and magnetism but remain difficult to realize. Breakthrough strategies could circumvent the mutually exclusive origins of magnetism and ferroelectricity by exploiting the interaction of multiple phonon modes in geometric improper and hybrid improper ferroelectrics. Yet, the proposed instability of a zone-boundary phonon mode, driving the emergence of ferroelectricity via coupling to a polar mode, remains to be directly observed. Here, we provide previously missing evidence for this scenario in the archetypal improper ferroelectric, yttrium manganite, through comprehensive scattering measurements of the atomic structure and phonons, supported with first-principles simulations. Our experiments and theoretical modeling resolve the origin of the unusual temperature dependence of the polarization and rule out a reported double-step ferroelectric transition. These results emphasize the critical role of phonon anharmonicity in rationalizing lattice instabilities in improper ferroelectrics and show that including these effects in simulations could facilitate the design of magnetoelectrics.
Authors:
ORCiD logo [1] ;  [2] ;  [3] ;  [4] ; ORCiD logo [4] ;  [4] ;  [5] ;  [3] ;  [1]
  1. Duke Univ., Durham, NC (United States). Dept. of Mechanical Engineering and Materials Science. Dept. of Physics; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division
  2. Duke Univ., Durham, NC (United States). Dept. of Mechanical Engineering and Materials Science. Dept. of Physics
  3. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Physics and Astronomy
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Neutron Scattering Division
  5. Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source
Publication Date:
Grant/Contract Number:
AC05-00OR22725; AC02-06CH11357; AC02-05CH11231; SC0016166; DMR-1350002
Type:
Accepted Manuscript
Journal Name:
Nature Communications
Additional Journal Information:
Journal Volume: 9; Journal ID: ISSN 2041-1723
Publisher:
Nature Publishing Group
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Duke Univ., Durham, NC (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ferroelectrics and multiferroics; phase transitions and critical phenomena
OSTI Identifier:
1427596
Alternate Identifier(s):
OSTI ID: 1461324