Search results for "Ferro"
showing 10 items of 2451 documents
Structure and Properties of Novel Pb(B’1/2Nb1/2)O3-PbTiO3 Binary Systems with High Piezoelectric Coupling
2000
The (l-x)Pb(Lu1/2Nb1/2)O3-xPbTiO3 (PLuNT) and (l-x)Pb(Er1/2Nb1/2)O3-xPbTiO3 (PErNT) binary systems have been originally synthesized. Pure lutecium niobate (PLuN) (x = 0) has a pronounced long-range order in the B-sublattice and an antiferroelectric to paraelectric phase transition at ~258°C. The phase structure of the PLuNT system, at room temperature, changes from a pseudomonoclinic (psd-M, space group Bmm2) to tetragonal (T, space group P4mm). The pseudomonoclinic phase extends over the 0 ≤ x ≤ 0.38 interval within which the monoclinic angle β proceeds a minimum near to 90° at x≅0.2. The morphotropic region covers over the interval x = 0.38–0.49, the concentration ratio psd-M:T≅l (the mor…
True Nanoferroics with the Properties Absent in Corresponding Bulk Samples
2013
The Chapter covers the theoretical and experimental approaches to the investigations of the physical properties, which are inherent in ferroics of nanosize and absent in corresponding bulk materials. Namely, the strong surface influence along with other effects of geometrical confinement generates number of physical effects, which do not occur in bulk ferroics samples. One example of such phenomena is room-temperature ferromagnetism in nanoparticles and thin films of undoped CeO2, HfO2, SnO2, Al2O3 and other nonmagnetic (in bulk samples) oxides. Theo other striking example is appearance of so-called spontaneous flexoeffects (i.e. flexoelectric, flexomagnetic, flexoelastic) in ferroic nanosa…
Long-distance spin-transport across the Morin phase transition up to room temperature in ultra-low damping single crystals of the antiferromagnet α-F…
2020
Antiferromagnetic materials can host spin-waves with polarizations ranging from circular to linear depending on their magnetic anisotropies. Until now, only easy-axis anisotropy antiferromagnets with circularly polarized spin-waves were reported to carry spin-information over long distances of micrometers. In this article, we report long-distance spin-transport in the easy-plane canted antiferromagnetic phase of hematite and at room temperature, where the linearly polarized magnons are not intuitively expected to carry spin. We demonstrate that the spin-transport signal decreases continuously through the easy-axis to easy-plane Morin transition, and persists in the easy-plane phase through …
Dielectric barrier discharge at the triglycine sulfate crystal surface: the role of the electric field of the domain structure
2014
Dielectric barrier discharges (DBD) at the triglycine sulfate crystal surface, generated in air under controlled gas pressure, have been investigated. Electrical characterization of these DBD discharges, produced at temperatures below as well as above the ferroelectric phase transition, are presented. The influence of the electric field of the domain structure on these DBD discharges are discussed in the frame of a model which takes into account the dynamics of the domain structure of the ferroelectric barrier under the action of an external voltage.
Spin transport across antiferromagnets induced by the spin Seebeck effect
2018
For prospective spintronics devices based on the propagation of pure spin currents, antiferromagnets are an interesting class of materials that potentially entail a number of advantages as compared to ferromagnets. Here, we present a detailed theoretical study of magnonic spin current transport in ferromagnetic-antiferromagnetic multilayers by using atomistic spin dynamics simulations. The relevant length scales of magnonic spin transport in antiferromagnets are determined. We demonstrate the transfer of angular momentum from a ferromagnet into an antiferromagnet due to the excitation of only one magnon branch in the antiferromagnet. As an experimental system, we ascertain the transport acr…
Epitaxial growth and properties of (001)-oriented TbBaCo2O6−δ films
2008
Thin epitaxial films of TbBaCo2O6−δ cobaltites have been synthesized using pulsed laser deposition. It was found that the film properties are extremely sensitive to the oxygen pressure during deposition, temperature of the substrate, and the cooling rate. Growth parameters were optimized for δ≈0.5 films with ordered Tb and Ba ions, as well as oxygen vacancies. The properties of these c-axis oriented films are similar to bulk TbBaCo2O5.5: they show a metal-insulator phase transition at TMI≈350 K, ferromagnetic order below TC=285 K, and antiferromagnetism at T<Ti≈230 K.
Synthesis of chloroantimonates(III) with selected organic cations. X-ray studies of phase transition in ferroelectric tris(trimethylammonium) nonachl…
2004
Abstract The dependence of molar ratio of reactants on the formula, crystal structure and physicochemical properties of chloroantimonates(III) with different organic cations was studied. It was proved, that the compounds show preferences in crystallization of one product. The changes of the molar ratio of substrates lead to the corresponding changes of these components in crystallized products. The structure of ferroelectric chloroantimonate(III), [(CH3)3NH]3[Sb2Cl9], was determined at 165 and 95 K. It crystallizes in monoclinic space group Pc: a=9.9612(11), b=9.0714(8), c=15.1807(14) A, β=90.086(8)°, R1=0.0202, wR2=0.0405 and a=9.9138(10), b=9.0783(7), c=15.1299(14) A, β=90.026(8)°, R1=0.0…
In situ study of the phase transition in Bi2Ti4O11
1995
Abstract The paraelectric ⇌ antiferroelectric phase transition of the compound Bi 2 Ti 4 O 11 is studied in situ by electron diffraction and electron microscopy. The transition is reversible and clearly second order. Above T c faint streaking at the superlattice positions persists. In the low-temperature phase, antiphase boundaries with a displacement vector R = 1/2[101] are revealed; they show a finite width, suggesting a gradual displacement of the Bi atoms at the transition. A model for the domain wall configuration is proposed, based on the influence of the lone pairs of Bi 3+ ions at the transition.
Critical effects in optical response due to charge transfer vibronic excitons and their structure in perovskite-like systems
1999
Abstract A mechanism for bilinear interaction between high-frequency light-induced electronic polarization and low-frequency soft lattice polarization is proposed. It is based on the fluctuations of the charge transfer connected with charge transfer vibronic excitons (CTVE). This bilinear mechanism leads to the appearance of the critical peculiarities of the absolute diffraction efficiency of transient gratings near the ferroelectric phase transition. A semi-empirical Hartree–Fock INDO method was used for the evaluation of the energy parameters and the equilibrium displacements for the CTVE in KTaO 3 . This numerical study did confirm the proposed CTVE-model. It was shown that the CTVE-phas…
Phase transitions in modified Na 1/2 Bi 1/2 TiO 3 ‐SrTiO 3 solid solutions
2009
Continuous transfer from relaxor to normal ferroelectric phase transition is found in Na1/2Bi1/2TiO3-SrTiO3-PbTiO3 if concentration of PbTiO3 increases. The relaxor properties in NBT solid solutions are described by the power law and Vogel-Fulcher relationship, and concentration dependence of the relevant parameters is discussed. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)