2 research outputs found
Magnetic Ordering-Induced Multiferroic Behavior in [CH<sub>3</sub>NH<sub>3</sub>][Co(HCOO)<sub>3</sub>] Metal–Organic Framework
We present the first example of magnetic
ordering-induced multiferroic
behavior in a metal–organic framework magnet. This compound
is [CH<sub>3</sub>NH<sub>3</sub>][Co(HCOO)<sub>3</sub>] with a perovskite-like
structure. The A-site [CH<sub>3</sub>NH<sub>3</sub>]<sup>+</sup> cation
strongly distorts the framework, allowing anisotropic magnetic and
electric behavior and coupling between them to occur. This material
is a spin canted antiferromagnet below 15.9 K with a weak ferromagnetic
component attributable to Dzyaloshinskii–Moriya (DM) interactions
and experiences a discontinuous hysteretic magnetic-field-induced
switching along [010] and a more continuous hysteresis along [101].
Coupling between the magnetic and electric order is resolved when
the field is applied along this [101]: a spin rearrangement occurs
at a critical magnetic field in the ac plane that induces a change
in the electric polarization along [101] and [10-1]. The electric
polarization exhibits an unusual memory effect, as it remembers the
direction of the previous two magnetic-field pulses applied. The data
are consistent with an inverse-DM mechanism for multiferroic behavior
[(CH<sub>3</sub>)<sub>2</sub>NH<sub>2</sub>]<sub>7</sub>Pb<sub>4</sub>X<sub>15</sub> (X = Cl<sup>–</sup> and Br<sup>–</sup>), 2D-Perovskite Related Hybrids with Dielectric Transitions and Broadband Photoluminiscent Emission
We have prepared
two new lead halides with the novel general formula of DMA<sub>7</sub>Pb<sub>4</sub>X<sub>15</sub> (DMA = [(CH<sub>3</sub>)<sub>2</sub>NH<sub>2</sub>]<sup>+</sup> and X = Cl<sup>–</sup> or Br<sup>–</sup>) by using an easy route under mild conditions at room
temperature. These compounds exhibit an unprecedented crystal structure,
are formed by layers of distorted [PbX<sub>6</sub>] octahedra, which
share corners and faces, and contain intercalated DMA cations. Very
interestingly, they display dielectric transitions, which are related
to a partial order–disorder process of the DMA cations between
160 and 260 K. Additionally, these new layered hybrids exhibit a broadband
photoluminiscent emission, which is related to the structural distortions
of the [PbX<sub>6</sub>] octahedra. These findings not only open up
large possibilities for future optoelectronic applications of these
materials, but they also offer a novel playground for an easy modulation
of electrical and optical properties of hybrid organic–inorganic
materials. We anticipate that this novel A<sub>7</sub>Pb<sub>4</sub>X<sub>15</sub> formula can be adequate to tune the family of the
hybrid lead halides using other alkylammonium cations, such as methylammonium,
formamidinium, or ethylammonium, to improve their photoelectronic
properties