20 research outputs found
Biferroic YCrO3
YCrO3 which has a monoclinic structure, shows weak ferromagnetism below 140 K
(TN) and a ferroelectric transition at 473 K accompanied by hysteresis. We have
determined the structure and energetics of YCrO3 with ferromagnetic and
antiferromagnetic ordering by means of first-principles density functional
theory calculations, based on pseudopotentials and a plane wave basis. The
non-centrosymmetric monoclinic structure is found to be lower in energy than
the orthorhombic structure, supporting the biferroic nature of YCrO3.Comment: 16 pages including figure
Multiferroic nature of charge-ordered rare earth manganites
Charge-ordered rare earth manganites Nd0.5Ca0.5MnO3, La0.25Nd0.25Ca0.5MnO3,
Pr0.7Ca0.3MnO3 and Pr0.6Ca0.4MnO3 are found to exhibit dielectric constant
anomalies around the charge-ordering or the magnetic transition temperatures.
Magnetic fields have a marked effect on the dielectric properties, indicating
the presence of coupling between the magnetic and electrical order parameters.
The observation of magnetoferroelectricity in these manganites is in accord
with the recent theoretical predictions of Khomskii and coworkers
Giant reversible nanoscale piezoresistance at room temperature in Sr2IrO4 thin films
Layered iridates have been the subject of intense scrutiny on account of
their unusually strong spin-orbit coupling, which opens up a narrow gap in a
material that would otherwise be a metal. This insulating state is very
sensitive to external perturbations. Here, we show that vertical compression at
the nanoscale, delivered using the tip of a standard scanning probe microscope,
is capable of inducing a five orders of magnitude change in the room
temperature resistivity of Sr2IrO4. The extreme sensitivity of the electronic
structure to anisotropic deformations opens up a new angle of interest on this
material, and the giant and fully reversible perpendicular piezoresistance
makes iridates a promising material for room temperature piezotronic devices
Single Crystal Functional Oxides on Silicon
Single crystalline thin films of complex oxides show a rich variety of
functional properties such as ferroelectricity, piezoelectricity, ferro and
antiferromagnetism etc. that have the potential for completely new electronic
applications (1-2). Direct synthesis of such oxides on Si remains challenging
due to the fundamental crystal chemistry and mechanical incompatibility of
dissimilar interfaces (3-16). Here we report integration of thin (down to 1
unit cell) single crystalline, complex oxide films onto Si substrates, by
epitaxial transfer at room temperature. In a field effect transistor using a
transferred Pb0.2Zr0.8TiO3 (PZT) layer as the gate insulator, we demonstrate
direct reversible control of the semiconductor channel charge with polarization
state. These results represent the realization of long pursued but yet to be
demonstrated single crystal functional oxides on-demand on silicon
New routes to multiferroics
Multiferroic materials are those which possess both ferroelectric and ferromagnetic properties. Clearly, there is a contradiction here since ferromagnetism requires d-electrons while ferroelectricity generally occurs only in the absence of d-electrons. Several multiferroics demonstrating magnetoelectric coupling effects have, however, been discovered in the past few years, but they generally make use of alternative mechanisms in attaining these properties. Several new ideas and concepts have emerged in the past two years, typical of them being magnetic ferroelectricity induced by frustrated magnetism, lone pair effect, charge-ordering and local non-centrosymmetry. Charge-order driven magnetic ferroelectricity is interesting in that it would be expected to occur in a large number of rare earth manganites, (A = alkaline earth), well known for colossal magnetoresistance, electronic phase separation and other properties. In this article, we discuss novel routes to multiferroics, giving specific examples of materials along with their characteristics
Multiferroic nature of charge-ordered rare earth manganites
Charge-ordered rare earth manganites , and are found to exhibit dielectric constant anomalies around the charge-ordering or the antiferromagnetic transition temperatures. Magnetic fields have a marked effect on the dielectric properties, indicating the presence of coupling between the magnetic and electrical order parameters. The observation of magnetoferroelectricity in these manganites is in accord with the recent theoretical predictions of Khomskii and co-worker
New routes to multiferroics
Multiferroic materials are those which possess both ferroelectric and ferromagnetic properties. Clearly, there is a contradiction here since ferromagnetism requires d-electrons while ferroelectricity generally occurs only in the absence of d-electrons. Several multiferroics demonstrating magnetoelectric coupling effects have, however, been discovered in the past few years, but they generally make use of alternative mechanisms in attaining these properties. Several new ideas and concepts have emerged in the past two years, typical of them being magnetic ferroelectricity induced by frustrated magnetism, lone pair effect, charge-ordering and local non-centrosymmetry. Charge-order driven magnetic ferroelectricity is interesting in that it would be expected to occur in a large number of rare earth manganites, Ln<SUB>1−x</SUB>A<SUB>x</SUB>MnO<SUB>3</SUB> (A=alkaline earth), well known for colossal magnetoresistance, electronic phase separation and other properties. In this article, we discuss novel routes to multiferroics, giving specific examples of materials along with their characteristics
Charge-order driven multiferroic and magneto-dielectric properties of rare earth manganates
Charge-order driven magnetic ferroelectricity is shown to occur in several rare earth manganates of the general formula, Ln(1-x)A(x)MnO(3) (In = rare earth, A = alkaline earth). Charge-ordered manganates exhibit dielectric constant anomalies around the charge-ordering or the antiferromagnetic transition temperature. Magnetic fields have a marked effect on the dielectric properties of these compounds, indicating the presence of coupling between the magnetic and electrical order parameters. Magneto-dielectric properties are retained in small particles of the manganates. The observation of magneto-ferroelectricity in these manganates is in accordance with theoretical predictions
Charge-order driven multiferroic and magneto-dielectric properties of rare earth manganates
Charge-order driven magnetic ferroelectricity is shown to occur in several rare earth manganates of the general formula, Ln(1-x)A(x)MnO(3) (In = rare earth, A = alkaline earth). Charge-ordered manganates exhibit dielectric constant anomalies around the charge-ordering or the antiferromagnetic transition temperature. Magnetic fields have a marked effect on the dielectric properties of these compounds, indicating the presence of coupling between the magnetic and electrical order parameters. Magneto-dielectric properties are retained in small particles of the manganates. The observation of magneto-ferroelectricity in these manganates is in accordance with theoretical predictions