Search results for "Ferro"
showing 10 items of 2451 documents
Neutron diffraction experiments on UCu4+xAl8−x
1992
Abstract Neutron diffraction experiments are reported on UCu4+xAl8−x for concentrations 0.1≤ x ≤1.9 and temperatures 1.6 K≤T≤300 K. For x ≤ 1 these compounds undergo antiferromagnetic phase transitions into a collinear AF I-type structure. with the magnetic moments aligned along the tetragonal c-axis and alternating order within the a−b planes. With increasing concentration the ordering temperatures decrease and moment compensation due to a Kondo-type interaction develops for x>1.
Structure and properties of high piezoelectric coupling Pb(B′½Nb½)O3-PbTiO3binary systems
1999
Abstract The (1-x)Pb(Lu½ Nb½)O3-xPbTiO3 and (1-x)Pb(Er½ Nb½)O3-xPbTiO3 binary systems have been obtained, the structure and properties of which are studied. The unit cell of erbium niobate (PErN) is described as pseudomonoclinic of orthorhombic Bmm2 symmetry: a=c=4.2161 A b=4.0869 A β=90.55° and composition is characterized with antiferroelectric phase transition at 305°C. The PErNT system has the morphotropic phase region extending over the x=0.4–0.6 interval. In PLuNT ceramics system the pseudomonoclinic phase structure Bmm2 extending over the 0≤x ≤0.38 interval becomes pseudocubic at x≈ 0.2. The morphotropic region is spread over 0.38< × < 0.49; at higher PT concentrations (1.0 ≥ × ≥ 0.4…
Quantum chemical modelling of perovskite solid solutions
2000
In line with our previous study (Eglitis R I et al 1998 J. Phys.: Condens. Matter 10 6271) for a single Nb impurity and Nb clusters in KTaO3 we present here the results of calculations for a series of perovskite KNbx Ta 1−x O3 (KTN) solid solutions (x = 0, 0.125, 0.25, 0.75, and 1). The quantum chemical method of the intermediate neglect of the differential overlap (INDO) combined with the large unit cell (LUC) periodic model is used. According to the INDO calculations, Nb impurity becomes off-centre in KTaO3 already at the lowest studied Nb concentration. Its off-centre displacement is in a good agreement with XAFS measurements. We compare our results with previous FP-LMTO calculations. Pe…
Vibrational Analysis of Paraelectric–Ferroelectric Transition of LiNbO3: An Ab-Initio Quantum Mechanical Treatment
2021
FSG acknowledges the CINECA award under the ISCRA initiative (HP10BJO47B) for the availability of high-performance computing resources and support.
Polymorphism in a π stacked Blatter radical: structures and magnetic properties of 3-(phenyl)-1-(pyrid-2-yl)-1,4-dihydrobenzo[ e ][1,2,4]triazin-4-yl
2020
International audience; 3-(Phenyl)-1-(pyrid-2-yl)-1,4-dihydrobenzo[e][1,2,4]triazin-4-yl (2) demonstrates the first example of polymorphism in the family of Blatter radicals. Two polymorphs, 2α and 2β, have been identified and characterized by single crystal X-ray diffractometry and magnetic susceptibility measurements to investigate their magnetism–structure correlations. Both polymorphs form one-dimensional (1D) π stacks of evenly spaced radicals with distinctly different π–π overlap modes. Within the 1D π stacks, radicals are located at evenly interplanar distances, 3.461 Å for 2α and 3.430 Å for 2β. Magnetic susceptibility studies indicate that both polymorphs exhibit antiferromagnetic …
Phonon superradiance and phonon laser effect in nanomagnets
2004
We show that the theory of spin-phonon processes in paramagnetic solids must take into account the coherent generation of phonons by the magnetic centers. This effect should drastically enhance spin-phonon rates in nanoscale paramagnets and in crystals of molecular nanomagnets.
Self-assembled monolayers based spintronics: from ferromagnetic surface functionalization to spin-dependent transport.
2016
Chemically functionalized surfaces are studied for a wide range of applications going from medicine to electronics. Whereas non-magnetic surfaces have been widely studied, functionalization of magnetic surfaces is much less common and has almost never been used for spintronics applications. In this article we present the functionalization of La2/3Sr1/3MnO3, a ferromagnetic oxide, with self-assembled monolayers for spintronics. La2/3Sr1/3MnO3 is the prototypical half-metallic manganite used in spintronics studies. First, we show that La2/3Sr1/3MnO3 can be functionalized by alkylphosphonic acid molecules. We then emphasize the use of these functionalized surfaces in spintronics devices such a…
Optical suppression of ferroelectricity in polysiloxane copolymers with chiral and photochromic side groups
1998
The ferroelectricity of surface-stabilized aligned films of polysiloxane copolymers containing chiral esters and photochromic azobenzene moieties within the side groups is suppressed on UV irradiation and is rebuilt on visible irradiation. The liquid crystalline polymer (Sc* 64 SA 80 i) shows ferroelectric behavior below 64°C. The photoinduced modification of supramolecular order and the corresponding changes in its dynamics are studied by polarized UV/vis spectroscopy and broad band dielectric spectroscopy (10−2–105 Hz). The dielectric measurements show that UV irradiation causes a loss of ferroelectricity within an interval of 10 K below the phase transition temperature. The photochemical…
High-sensitive switchable photodetector based on BiFeO3 film with in-plane polarization
2015
A high-sensitive and fast-response photodetector based on BiFeO3 (BFO) ferroelectric thin film is fabricated using coplanar electrode configuration. A large photocurrent/dark current ratio is found up to two orders of magnitude at 1 V bias. Enhanced photocurrent and rectification behavior of the photodetector are observed after applying high voltage pulses to the BFO film. The short-circuit current varies systematically with the poling process and increases linearly with the light density. On the contrary, the open-circuit voltage keeps as a constant during the measurements. We attribute these behaviors to the depolarization field and the interfacial fields at the film-electrode interfaces.…
Photoelectric Current and Dielectric Properties of Barium-Strontium Niobate Ceramics under UV and Visible Irradiation
2015
A study of photocurrent kinetics and dielectric response to infra-low frequencies in the range of the broad phase transition in the Ba0.25Sr0.75Nb2O6 (BSN-75) relaxor ceramics under visible and ultraviolet radiation is reported. Anomalies are revealed in the dependence on field intensity of dielectric permittivity and dielectric loss determined from measurements of polarisation loops before and after illumination. The effects of pyro-electric space charge, polarisation and photovoltaic contributions on behaviour of the measured photocurrent are discussed. Results of the kinetics of photocurrent and dielectric response to infra-low frequency studied at different temperatures are discussed as…