Search results for "Phase transition"
showing 10 items of 1281 documents
Thermodynamic properties at the phase transition of Pb(Zr, Sn, Ti)O3solid solutions
2000
Abstract Field induced deformation and electrocaloric effect are investigated in the vicinity of phase transition at 163°C. The sharp increase of electrostriction below Tc is explained by the field induced ferroelectric to antiferroelectric phase transition. The antiferroelectric phase appears and remains stable below Tc in the absence of field. Elastic compliance and thermal expansion as functions of temperature are studied.
Relation between deformation and polarization in the region of diffused phase transition of plzt 8/65/35
1995
Abstract The deformation as a function of polarization was measured in PLZT 8-10/65/35 in the region of diffused phase transition. A different behaviour of deformation in the region of double hysteresis loops was observed corresponding to ferroelectric and nonpolar phases as well as to the field induced phase transition region. In the ferroelectric phase the results are described by electrostriction. The decrease of volume as well as small longitudinal deformations at the field induced transition to ferroelectric state are explained by large remanent deformations, existing in the nonpolar phase. Since description of deformation in the framework of electrostriction cannot be motivated in the…
Experimental evidence for a local disorder in pure and doped perovskites
1992
Abstract In the soft mode picture, the ferroelectric phase transitions in most of ABO3 perovskites are triggered by the long wavelength oscillations of the B ions against their oxygen cage. There is now a lot of experimental evidence that this picture is incomplete. An extra contribution has to be included in the dynamical response. This contribution is usually thought to arise from local lattice distorsions; this is what will be called local disorder. A complete understanding of this local disorder requires the experimental determination of the microscopic origin, of the dynamics and spatial extension of the lattice distorsions. A useful way to summarize these requirements is to use the co…
Magnetic field tuning of the smart materials domain structure
1998
The investigation of the behavior of the ferroelectric phase transition with magnetic filed tuning and concentration change is highly attractive owing to the possibility to prepare alloying samples and to predict theoretically the parameters of the magnetic field and concentration response at relatively small concentrations. These parameters may be extracted from the equation of states of the perovskite under investigation in the assumption of the linear response. The study of the movement of the paraelectric - ferroelectric interphase boundary in (Ba,Sr)TiO 3 with concentration change and in constant magnetic fields is provided in the framework of the mean-field theory. The analytical solu…
Phase transitions of Pb0.99Nb0.02(Zr0.75Sn0.20Ti0.05)O3ceramics
2001
Abstract The dielectric, elastic and electromechanical properties, electrocaloric effect and thermal expansion of poled and depoled Pb0.99Nb0.02(Zr0.75Sn0.20Ti0.05)O3 samples are presented to evaluate the nature of polar phases existing in the solid solution above room temperature. The Kittel's free energy expansion is used to explain some essential features of physical properties.
Monte Carlo Simulations of Alloy Phase Transformations
1994
The use of Monte Carlo simulation methods for study of order-disorder phase transitions in lattice models of alloys is reviewed, with an emphasis on interfacial phenomena and the kinetics of ordering and/or phase separation. Topics discussed include the attempt to predict the phase diagram of Fe-Al alloys from recent measurements of effective interaction parameters, competition between magnetic and crystallographic ordering in such alloys, and the structure of their antiphase domain boundaries. Both an interfacial roughening transition of this domain wall and interfacial enrichment phenomena are predicted. Then simulations of alloy-vacuum surfaces are discussed, and it is shown that both ca…
Structure of metastable 2D liquid helium
2007
We present diffusion Monte Carlo (DMC) results on a novel, superfluid phase in two-dimensional 4He at densities higher than 0.065 A-2, which is very close to the freezing density. The new phase has anisotropic, hexatic orbital order, but the single-particle density remains constant. By increasing density the hexatic superfluid forms a metastable state, which lies above the crystal ground state in energy. This implies that the liquid-solid phase transition takes place in two stages: a second-order phase transition from the isotropic superfluid to the hexatic superfluid, followed by a first-order transition that localizes atoms into the triangular crystal order.
Strong-coupling phases of the spin-orbit-coupled spin-1 Bose-Hubbard chain: Odd-integer Mott lobes and helical magnetic phases
2017
We study the odd integer filled Mott phases of a spin-1 Bose-Hubbard chain and determine their fate in the presence of a Raman induced spin-orbit coupling which has been achieved in ultracold atomic gases; this system is described by a quantum spin-1 chain with a spiral magnetic field. The spiral magnetic field initially induces helical order with either ferromagnetic or dimer order parameters, giving rise to a spiral paramagnet at large field. The spiral ferromagnet-to-paramagnet phase transition is in a novel universality class, with critical exponents associated with the divergence of the correlation length $\nu \approx 2/3$ and the order parameter susceptibility $\gamma \approx 1/2$. We…
Magnetic quantum criticality in quasi-one-dimensional Heisenberg antiferromagnet Cu (C4H4N2)( NO 3)2
2016
We analyze exciting recent measurements [Phys. Rev. Lett. 114 (2015) 037202] of the magnetization, differential susceptibility and specific heat on one dimensional Heisenberg antiferromagnet Cu(C4H4N2)(NO3)2 (CuPzN) subjected to strong magnetic fields. Using the mapping between magnons (bosons) in CuPzN and fermions, we demonstrate that magnetic field tunes the insulator towards quantum critical point related to so-called fermion condensation quantum phase transition (FCQPT) at which the resulting fermion effective mass diverges kinematically. We show that the FCQPT concept permits to reveal the scaling behavior of thermodynamic characteristics, describe the experimental results quantitativ…
Identification of strongly correlated spin liquid in herbertsmithite
2011
Exotic quantum spin liquid (QSL) is formed with such hypothetic particles as fermionic spinons carrying spin 1/2 and no charge. Here we calculate its thermodynamic and relaxation properties. Our calculations unveil the fundamental properties of QSL, forming strongly correlated Fermi system located at a fermion condensation quantum phase transition. These are in a good agreement with experimental data and allow us to detect the behavior of QSL as that observed in heavy fermion metals. We predict that the thermal resistivity of QSL under the application of magnetic fields at fixed temperature demonstrates a very specific behavior. The key features of our findings are the presence of spin-char…