Abstract
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.
| Original language | English |
|---|---|
| Article number | 15 |
| Journal | Nature Communications |
| Volume | 9 |
| Issue number | 1 |
| DOIs | |
| State | Published - Dec 1 2018 |
Funding
We thank O. Hellman for providing and helping to use the TDEP software, C. Luo for help with XRD measurements, B.S. Lokitz for help with thermogravimetric analysis, W. Porter for initial testing of samples at high-T under different environmental conditions in DSC, and R. Mills for technical support with the high-temperature furnace. Neutron and x-ray scattering measurements and analysis were supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division, under the Early Career Award No. DE-SC0016166. H.Z. (sample synthesis) thanks the support from NSF-DMR-1350002. The use of Oak Ridge National Laboratory’s Spallation Neutron Source and High Flux Isotope Reactor was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. DOE. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. Thermogravimetric analysis was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. Theoretical calculations were performed using resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the US Department of Energy under contract no. DE-AC02-05CH11231. This manuscript has been co-authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).
| Funders | Funder number |
|---|---|
| DOE Office of Science | |
| NSF-DMR-1350002 | |
| Office of Basic Energy Sciences | |
| Scientific User Facilities Division | |
| U.S. DOE | |
| US Department of Energy | DE-AC05-00OR22725 |
| U.S. Department of Energy | |
| Office of Science | |
| Basic Energy Sciences | |
| Argonne National Laboratory | |
| Oak Ridge National Laboratory | |
| Division of Materials Sciences and Engineering |