6 research outputs found
Single Sublattice Endotaxial Phase Separation Driven by Charge Frustration in a Complex Oxide
Complex
transition-metal oxides are important functional materials
in areas such as energy and information storage. The cubic ABO<sub>3</sub> perovskite is an archetypal example of this class, formed
by the occupation of small octahedral B-sites within an AO<sub>3</sub> network defined by larger A cations. We show that introduction of
chemically mismatched octahedral cations into a cubic perovskite oxide
parent phase modifies structure and composition beyond the unit cell
length scale on the B sublattice alone. This affords an endotaxial
nanocomposite of two cubic perovskite phases with distinct properties.
These locally B-site cation-ordered and -disordered phases share a
single AO<sub>3</sub> network and have enhanced stability against
the formation of a competing hexagonal structure over the single-phase
parent. Synergic integration of the distinct properties of these phases
by the coherent interfaces of the composite produces solid oxide fuel
cell cathode performance superior to that expected from the component
phases in isolation
Room Temperature Magnetically Ordered Polar Corundum GaFeO<sub>3</sub> Displaying Magnetoelectric Coupling
The
polar corundum structure type offers a route to new room temperature
multiferroic materials, as the partial LiNbO<sub>3</sub>-type cation
ordering that breaks inversion symmetry may be combined with long-range
magnetic ordering of high spin <i>d</i><sup>5</sup> cations
above room temperature in the <i>A</i>FeO<sub>3</sub> system.
We report the synthesis of a polar corundum GaFeO<sub>3</sub> by a
high-pressure, high-temperature route and demonstrate that its polarity
arises from partial LiNbO<sub>3</sub>-type cation ordering by complementary
use of neutron, X-ray, and electron diffraction methods. In situ neutron
diffraction shows that the polar corundum forms directly from AlFeO<sub>3</sub>-type GaFeO<sub>3</sub> under the synthesis conditions. The <i>A</i><sup>3+</sup>/Fe<sup>3+</sup> cations are shown to be more
ordered in polar corundum GaFeO<sub>3</sub> than in isostructural
ScFeO<sub>3</sub>. This is explained by DFT calculations which indicate
that the extent of ordering is dependent on the configurational entropy
available to each system at the very different synthesis temperatures
required to form their corundum structures. Polar corundum GaFeO<sub>3</sub> exhibits weak ferromagnetism at room temperature that arises
from its Fe<sub>2</sub>O<sub>3</sub>-like magnetic ordering, which
persists to a temperature of 408 K. We demonstrate that the polarity
and magnetization are coupled in this system with a measured linear
magnetoelectric coupling coefficient of 0.057 ps/m. Such coupling
is a prerequisite for potential applications of polar corundum materials
in multiferroic/magnetoelectric devices
Room Temperature Magnetically Ordered Polar Corundum GaFeO<sub>3</sub> Displaying Magnetoelectric Coupling
The
polar corundum structure type offers a route to new room temperature
multiferroic materials, as the partial LiNbO<sub>3</sub>-type cation
ordering that breaks inversion symmetry may be combined with long-range
magnetic ordering of high spin <i>d</i><sup>5</sup> cations
above room temperature in the <i>A</i>FeO<sub>3</sub> system.
We report the synthesis of a polar corundum GaFeO<sub>3</sub> by a
high-pressure, high-temperature route and demonstrate that its polarity
arises from partial LiNbO<sub>3</sub>-type cation ordering by complementary
use of neutron, X-ray, and electron diffraction methods. In situ neutron
diffraction shows that the polar corundum forms directly from AlFeO<sub>3</sub>-type GaFeO<sub>3</sub> under the synthesis conditions. The <i>A</i><sup>3+</sup>/Fe<sup>3+</sup> cations are shown to be more
ordered in polar corundum GaFeO<sub>3</sub> than in isostructural
ScFeO<sub>3</sub>. This is explained by DFT calculations which indicate
that the extent of ordering is dependent on the configurational entropy
available to each system at the very different synthesis temperatures
required to form their corundum structures. Polar corundum GaFeO<sub>3</sub> exhibits weak ferromagnetism at room temperature that arises
from its Fe<sub>2</sub>O<sub>3</sub>-like magnetic ordering, which
persists to a temperature of 408 K. We demonstrate that the polarity
and magnetization are coupled in this system with a measured linear
magnetoelectric coupling coefficient of 0.057 ps/m. Such coupling
is a prerequisite for potential applications of polar corundum materials
in multiferroic/magnetoelectric devices
A Polar Corundum Oxide Displaying Weak Ferromagnetism at Room Temperature
Combining long-range magnetic order with polarity in
the same structure
is a prerequisite for the design of (magnetoelectric) multiferroic
materials. There are now several demonstrated strategies to achieve
this goal, but retaining magnetic order above room temperature remains
a difficult target. Iron oxides in the +3 oxidation state have high
magnetic ordering temperatures due to the size of the coupled moments.
Here we prepare and characterize ScFeO<sub>3</sub> (SFO), which under
pressure and in strain-stabilized thin films adopts a polar variant
of the corundum structure, one of the archetypal binary oxide structures.
Polar corundum ScFeO<sub>3</sub> has a weak ferromagnetic ground state
below 356 Kthis is in contrast to the purely antiferromagnetic
ground state adopted by the well-studied ferroelectric BiFeO<sub>3</sub>
A Polar Corundum Oxide Displaying Weak Ferromagnetism at Room Temperature
Combining long-range magnetic order with polarity in
the same structure
is a prerequisite for the design of (magnetoelectric) multiferroic
materials. There are now several demonstrated strategies to achieve
this goal, but retaining magnetic order above room temperature remains
a difficult target. Iron oxides in the +3 oxidation state have high
magnetic ordering temperatures due to the size of the coupled moments.
Here we prepare and characterize ScFeO<sub>3</sub> (SFO), which under
pressure and in strain-stabilized thin films adopts a polar variant
of the corundum structure, one of the archetypal binary oxide structures.
Polar corundum ScFeO<sub>3</sub> has a weak ferromagnetic ground state
below 356 Kthis is in contrast to the purely antiferromagnetic
ground state adopted by the well-studied ferroelectric BiFeO<sub>3</sub>
A Polar Corundum Oxide Displaying Weak Ferromagnetism at Room Temperature
Combining long-range magnetic order with polarity in
the same structure
is a prerequisite for the design of (magnetoelectric) multiferroic
materials. There are now several demonstrated strategies to achieve
this goal, but retaining magnetic order above room temperature remains
a difficult target. Iron oxides in the +3 oxidation state have high
magnetic ordering temperatures due to the size of the coupled moments.
Here we prepare and characterize ScFeO<sub>3</sub> (SFO), which under
pressure and in strain-stabilized thin films adopts a polar variant
of the corundum structure, one of the archetypal binary oxide structures.
Polar corundum ScFeO<sub>3</sub> has a weak ferromagnetic ground state
below 356 Kthis is in contrast to the purely antiferromagnetic
ground state adopted by the well-studied ferroelectric BiFeO<sub>3</sub>