Phonon localization drives polar nanoregions in a relaxor ferroelectric.
Relaxor ferroelectrics exemplify a class of functional materials where interplay between disorder and phase instability results in inhomogeneous nanoregions. Although known for about 30 years, there is no definitive explanation for polar nanoregions (PNRs). Here we show that ferroelectric phonon localization drives PNRs in relaxor ferroelectric PMN-30%PT using neutron scattering. At the frequency of a preexisting resonance mode, nanoregions of standing ferroelectric phonons develop with a coherence length equal to one wavelength and the PNR size. Anderson localization of ferroelectric phonons by resonance modes explains our observations and, with nonlinear slowing, the PNRs and relaxor properties. Phonon localization at additional resonances near the zone edges explains competing antiferroelectric distortions known to occur at the zone edges. Our results indicate the size and shape of PNRs that are not dictated by complex structural details, as commonly assumed, but by phonon resonance wave vectors. This discovery could guide the design of next generation relaxor ferroelectrics.
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
M E
ME
Manley
NIST Center for Neutron Research, National Institute of Technology (NIST), Gaithersburg, Maryland 20899, USA.
J W
JW
Lynn
Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
D L
DL
Abernathy
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
E D
ED
Specht
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
O
O
Delaire
Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
A R
AR
Bishop
TRS Technologies, State College, Pennsylvania 16801, USA.
R
R
Sahul
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
J D
JD
Budai
D003460:Crystallization; D004560:Electricity; D058085:Iron Compounds / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry*; D033363:Neutron Diffraction; D060739:Phonons; D014961:X-Ray Diffraction
D058085:Iron Compounds