3 research outputs found
What Determines the Critical Electric Field of AFE-to-FE in Pb(Zr,Sn,Ti)O<sub>3</sub>‑Based Perovskites?
Electric-field-induced antiferroelectric-ferroelectric
(AFE-FE)
phase transition is a prominent feature of antiferroelectric (AFE)
materials. The critical electric field of this phase transition is
crucial for the device performance of AEFs in many applications, but
the determining factor of the critical electric field is still unclear.
Here, we have established the correlation between the underlying structure
and the critical electric field by using in situ synchrotron
X-ray diffraction and high-resolution neutron diffraction in Pb(Zr,Sn,Ti)O3-based antiferroelectrics. It is found that the critical electric
field is determined by the angle between the average polarization
vector in the incommensurate AFE state and the [111]P polarization
direction in the rhombohedral FE state. A large polarization rotation
angle gives rise to a large critical electric field. Further, density
functional theory (DFT) calculations corroborate that the lower energy
is required for driving a smaller angle polarization rotation. Our
discovery will offer guidance to optimize the performance of AFE materials
Atomic Mechanism of Hybridization-Dependent Surface Reconstruction with Tailored Functionality in Hexagonal Multiferroics
The
broken symmetry along with anomalous defect structures and charging
conditions at multiferroics surface can alter both crystal structures
and electronic configurations, bringing in emergent physical properties.
Extraordinary surface states are induced into original mutually coupled
order parameters in such strongly correlated oxides, which flourish
in diverse properties but remain less explored. Here, we report the
peculiar surface ferroelectric states and reconfigurable functionalities
driven by the relaxation of surface and consequent changes in O 2p
and Y 4d orbital (p–d) hybridization within a representative
hexagonal multiferroics, YMnO<sub>3</sub>. An unprecedented surface
reconstruction is achieved by tailored p–d hybridization coupling
with in-plane oxygen vacancies, which is atomically revealed on the
basis of the advantages of state-of-the-art aberration-corrected (scanning)
transmission electron microscopy. Further ab initio density functional
theory calculations verify the key roles of in-plane oxygen vacancies
in modulating polarization properties and electronic structure, which
should be regarded as the atomic multiferroic element. This surface
configuration is found to induce tunable functionalities, such as
surface ferromagnetism and conductivity. Meanwhile, the controversial
origin of improper ferroelectricity that is unexpectedly free from
critical size has also been atomically unraveled. Our findings provide
new insights into the design and implementation of surface chemistry
devices by simply controlling the oxygen stoichiometry, greatly advance
our understandings of surface science in strongly correlated oxides,
and enable exciting innovations and new technological functionality
paradigms
Emergent Three-Dimensional Electric Dipole Sinewave in Bulk Perovskite Oxides
The magnetic and electric dipoles of ferroics play a
central role
in their fascinating properties. In particular, topological configurations
have shown promising potential for use in novel electromechanical
and electronic devices. Magnetic configurations from simple collinear
to complex topological are well-documented. In contrast, many complex
topological features in the electric counterpart remain unexplored.
Here, we report the first example of three-dimensional electric dipole
sinewave topological structure in a PbZrO3-based bulk perovskite,
which presents an interesting triple-hysteresis loop macroscopically.
This polar configuration consists of two orthogonal sinewave electric
dipole modulations decoded from a polar incommensurate phase by advanced
diffraction and atomic-resolution imaging techniques. The resulting
topology is unraveled to be the competition between the antiferroelectric
and ferroelectric states, stabilized by the modulation of the Pb 6s2 lone pair and the antiferrodistortive effect. These findings
further reinforce the similarity of the magnetic and electric topologies