Polarization Of Pb Research Articles

Measurements of quarkonium production and polarization in Pb–Pb collisions with ALICE

Quarkonia are excellent probes of deconfinement in heavy-ion collisions. For J/ψ, a bound state of cc¯ quarks, the (re-)generation is found to be the dominant production mechanism at the LHC energies. Production measurements of non-prompt J/ψ, originating from beauty-hadron decays, allow one to access the interaction of beauty-quarks with the quark-gluon plasma (QGP). Polarization and spin alignment measurements can be used to investigate the characteristics of the formed medium. Moreover, it has been hypothesized that quarkonium states can be polarized by the strong magnetic field generated in the initial state of the collision and by the large angular momentum of the medium in non-central heavy-ion collisions. In these proceedings, the measurements of the inclusive, prompt, and non-prompt J/ψ nuclear modification factor RAA in Pb–Pb collisions at √SNN = 5.02 TeV are shown. The measured non-prompt J/ψ fraction extends down to very low pT with a significantly improved precision compared to previous publications. The results from the first publication on the J/ψ polarization with respect to the event-plane in Pb–Pb collisions at √SNN = 5.02 TeV at forward rapidity are presented as well. The results are compared with available calculations.

Vector Mesons Polarization in Pb–Pb and \(pp\) Collisions with ALICE

Vector Mesons Polarization in Pb–Pb and \(pp\) Collisions with ALICE

Quarkonia as probes of the QGP and of the initial stages of the heavy-ion collision with ALICE

Studies of quarkonium production in heavy-ion collisions can be used for probing QGP properties. The suppression and regeneration of bound quarkonium states is sensitive to the medium properties. Modifications of the quarkonium polarization in Pb–Pb collisions with respect to pp collisions may give further insight into the suppression and regeneration mechanisms in the QGP. Quarkonia are also sensitive to the initial stages of heavy-ion collisions, and measurements in photonuclear collisions may help constrain the nuclear gluon-distribution at low Bjorken-x. In this work, recent quarkonium measurements performed by ALICE in Pb–Pb collisions at √SNN = 5.02 TeV will be discussed. Preliminary measurements of the inclusive J/ψ RAA measured at both forward and central rapidity will be presented. The J/ψ polarization measured for the first time in Pb–Pb collisions, as well as preliminary measurements of the coherent J/ψ photoproduction cross section, will be discussed.

Temperature–field phase diagram and spontaneous polarization in Pb(Sc1/2Ta1/2)O3 single crystal

The temperature–field phase diagram and the temperature dependence of the spontaneous polarization in Pb(Sc1/2Ta1/2)O3 (PST) have been investigated by measuring the permittivity in the dc biasing field and observing the p–E hysteresis loop, respectively. X-ray diffraction studies to clarify the B-site cation ordering have also been performed. We have confirmed the PST single crystal used in our experiment to be a disordered PST. We have also determined that the ferroelectric critical endpoint (CEP) on the temperature–field phase diagram in the dc biasing field applied along the [111]c direction (in the cubic coordinate) was at 19.3 °C and 4.85 kV cm−1. Our experimental results of the ferroelectric CEP and the spontaneous polarization in disordered PST are discussed in this paper on the basis of the Landau-type phenomenological theory.

Magnetic properties of L10 FePt thin film influenced by recoverable strains stemmed from the polarization of Pb(Mg1/3Nb2/3)O3–PbTiO3 substrate**Project supported by the National Natural Science Foundation of China (Grant Nos. 11474167, 51701091, and 11504020) and the Start-up Funds of NUIST, China (Grant Nos. 2243141601035 and 2243141601018).

The magnetic properties and magnetization reversible processes of L10 FePt (3 nm)/Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) heterostructure were investigated by using the phase field model. The simulation results show that the magnetic coercivities and magnetic domains evolution in the L10 FePt thin film are significantly influenced by the compressive strains stemming from the polarization of single crystal PMN–PT substrate under an applied electric field. It is found that the magnetic coercivities increase with increasing of the compressive strain. A large compressive strain is beneficial to aligning the magnetic moments along the out-of-plane direction and to the enhancement of perpendicular magnetic anisotropy. The variations of magnetic energy densities show that when compressive strains are different at the magnetization reversible processes, the magnetic anisotropy energies and the magnetic exchange energies firstly increase and then decrease, the negative demagnetization energy peaks appear at coercivities fields, and the magnetoelastic energies are invariable at large external magnetic field with the energy maximum appearing at coercivities fields. The variations of the magnetoelastic energies bring about the perpendicular magnetic anisotropy so that the magnetoelastic energy is lower at the large external magnetic fields, whereas the appearance of magnetoelastic energy peaks is due to the magnetization-altered direction from the normal direction of the plane of the L10 FePt thin film at coercivities fields.

Two Components of the Macroscopic Polarization in Pb(Mg1/3Nb2/3)O3 Relaxor Ferroelectric

A pyroelectric charge measurement was carried out for Pb(Mg1/3Nb2/3)O3 over the wide temperature range from 80 to 475 K. Macroscopic polarization was observed up to 420 ± 30 K, with marked changes at approximately 200 and 420 K. The first component of a polarization developing below 200 K is about 20 µC/cm2, and the second component developing below 420 K is about 4 µC/cm2. These components can be observed together or selectively depending on field cooling conditions, indicating that these components have respective origins that are different from each other. The results provide direct evidence of the occurrence of the static polar nanoregion below around 420 K.

Manganese effect on the relaxation behaviors of the space charge polarization in Pb(Fe 2/3W 1/3) 0.9Ti 0.1O 3 ceramics

The effects of manganese on the space charge polarization in 0.9Pb(Fe 2/3W 1/3)O 3–0.1PbTiO 3 (0.9PFW–0.1PT) ceramics are discussed using the Debye theory and the Arrhenius law. The static dipole moment of the space charge polarization is decreased by the MnO additives. The values of the Debye relaxation time τ 0 and the activation energy E τ of the space charge polarization are similar at any temperature range before adding MnO. These values are changed after adding MnO and are obviously changed only at the lower temperature range. According to these results, it is suggested that the space charge polarizations are induced due to the charge imbalance in the micropolarization region and the conductive carriers. The charge imbalance and the conductive carriers are reduced by adding MnO additives since the compositional fluctuation is restrained and the electronic compensation is induced.

Self Polarization in Pb(Sc1/2Ta1/2)O3 Relaxor Thin Films: Impact on the Dielectric and Piezoelectric Response

The phenomenon of “self-polarization” was studied in chemical solution derived Pb(Sc1/2Ta1/2)O3 (PST) thin films on Pt/Si substrates. PST films exhibited field induced pyroelectric coefficients of 300 µC/(m2 K), with a detectivity figure of merit Fd=1.5×10-5 Pa-1/2 at 100 kV/cm bias fields. The piezoelectric coefficient d33 was found to saturate at a value of 60 pm/V at 100 kV/cm applied field and the electrostriction coefficient Q33 was found to be ∼0.025 m4/C2. The presence of self polarization was confirmed by piezoelectric and pyroelectric activity under zero applied bias fields, resulting in a pyroelectric coefficient of 50 µC/(m2 K), or an equivalent internal field of ∼25 kV/cm. The impact of this internal bias field on the dielectric constant at temperatures near the dielectric maximum corresponds to a ∼10% reduction in the dielectric constant. It is concluded that the “self-polarization” observed in relaxor PST films cannot be the origin of the order of magnitude reduction in the dielectric constant of thin films as compared to ceramics.

Electrical Properties of Perovskite-Based Ferroelectric Thin Films Modified Using Rare-Earth Elements

The electrical properties of perovskite-based ferroelectric films were improved by ion modification using rare-earth cations. Thin films of rare-earth-modified lead zirconate titanate [Pb(Zr,Ti)O3] were fabricated on (111)Pt/Ti/SiO2/(100)Si substrates by a chemical solution deposition technique. The substitution of volatile cations in the simple-perovskite oxides, such as Pb2+ in Pb(Zr,Ti)O3 films, enhanced the insulating properties of the film. The crystal anisotropy of the Pb(Zr,Ti)O3 film could be controlled by varying the species and the amount of replacing cations to enhance the spontaneous polarization. Thus, ion modification using Dy3+ cation could enhance the remanent polarization of Pb(Zr,Ti)O3 film consequently.

Imaging of ferroelectric polarization in Pb(Mg1∕3Nb2∕3)O3–PbTiO3 crystals by scanning electro-optic microscopy

Spatial distribution of the ferroelectric polarization in (1−x)Pb(Mg1∕3Nb2∕3)O3–xPbTiO3 single crystals with x=0.25 has been visualized using scanning confocal electro-optic microscopy. Domains showing different values and signs of the linear electro-optic effect are observed in both ⟨001⟩ and ⟨111⟩ oriented crystal plates in case of application of a symmetry-breaking dc electric field. Features of the observed images are explained on the basis of the electro-optic tensor analysis.

Bilateral switching of the modulated electrooptic contrast in PLZTN ceramics

Spatial distribution of ferroelectric polarization in Pb(Zr,Ti)O 3 ceramics doped with lanthanum and niobium has been investigated using scanning electrooptic confocal microscopy. Measurement of the modulated electrooptic signal in presence of a sinusoidal electric field reveals ferroelectric domains at microscopic scale not accessible to conventional polarized optical imaging. Both electrooptic images and local electrooptic loops have been observed after applying a bias electric field to the ceramic samples, being initially non-ferroelectric macroscopically. Bilateral reversal of the electrooptic contrast during the poling cycle has been detected and explained taking into account non-180° switching processes in ferroelectric grains of arbitrary orientation.

Relaxation of Remanent Polarization in Pb(Zr,Ti)O3 Thin Film Capacitors

The retained charge (memory window) of a ferroelectric capacitor measured by the pulse method is smaller than that measured by the continuous wave method. This is attributed to the relaxation phenomenon which represents the fast loss of the remanent polarization after removal of the applied voltage. The relaxation phenomenon is induced by the depolarization field which is affected by various parameters such as the ferroelectric properties and thickness of the ferroelectric film, measurement temperature, electrode material and the formation of an interfacial layer between the ferroelectric film and the electrodes. In this study, the effects of each parameter and the causes of the relaxation phenomenon were investigated. The magnitude of polarization loss increases with that of the initial remanent polarization. The increased polarization loss with increasing measurement temperature is attributed to the reduced coercive field with temperature. The fatigue stressing and the use of a RuO2 top electrode cause the formation of a nonswitching interfacial layer between the ferroelectric film and the electrodes, resulting in the large relaxation and thus large polarization loss. The reduction in the thickness of the ferroelectric film also results in the increasing polarization loss by increasing the magnitude of the depolarization field.

Substrate Influence on the Reversible and Irreversible Polarization Contributions in Ferroelectric Thin Films

ABSTRACTIn this contribution, the influence of different substrates and textures on the reversible and irreversible polarization in Pb(Zr,Ti)O3 (PZT) thin films will be presented. One possible scenario to explain the origin of the ferroelectric hysteresis is the notion that the domain walls move through a potential generated by their interaction with randomly distributed defects of the matrix. This potential then gives rise to reversible and irreversible changes in the ferroelectric polarization. The exact features of the interaction potential also depend on the stress state of the material which can be influenced by a suitable choice of the substrate.To study the substrate influence, PZT thin films have been deposited on commercial Si wafers, MgO and SrTiO3 single crystals. Electrical characterization methods (hysteresis and small signal capacitance measurements) have been used to extract information on reversible and irreversible polarization contributions.

Electrostrictive properties and polarization mechanisms of Pb(Zn1/3Nb2/3)O3 based ceramics

Both the electrostrictive strain and electric polarization of Pb(Zn1/3Nb2/3)O3-BaTiO3-PbTiO3 ceramics near MPB were carefully measured as a function of electric field strength, and temperature. The longitudinal strain versus the polarization squared with varying compositions was also analyzed. In terms of their domain structure and x-ray diffraction pattern under different dc bias, the field-induced domain switching and polarization mechanism of ferroelectric ceramics is discussed. It should be stressed that microdomains and macrodomains each provide a different contribution to the field-induced strain.

Non-uniform distribution of polarization in Pb 0.76 Ca 0.24 (Co 0.5 W 0.5 ) 0.05 Ti 0.95 O 3 ceramics produced by defects

Polarization distribution of calcium-modified lead titanate ceramics with a nominal composition of Pb0.76Ca0.24(Co0.5W0.5)0.05Ti0.95O3 was measured from the thermocurrents stimulated in these materials by a sinusoidal thermal wave. The polarization distribution was obtained and related to the development of defects in the material during processing. The deviation in the perovskite composition and the formation of segregated phases at the grain boundaries have been studied using the techniques of energy dispersion X-ray analysis, scanning electron microscopy and backscattering electron analysis.

Ring-disk electrode studies of soluble intermediates formed during the polarization of Pb in H 2SO 4

The use of a rotating ring-disk electrode to detect soluble Pb(1V) and Pb(11) species released into H 2SO 4 has made it possible to give complementary interpretations for the processes occuring during the anodization and successive reduction of Pb electrodes. It has been shown that soluble Pb(1V) species act as intermediates during the formation tetravalent oxides of Pb, and that the generation of tetravalent products is always preceded by the information of divalent products even at high positive potentials. During the reduction of PbO 2, species are released. Part of the tetravalent products formed at Pb are reduced only at high negative potentials.

Influence of hydrostatic pressure on phase transitions and remnant polarization in Pb(Zr1-xTix)O3solid solutions

Abstract The temperature dependence of remnant polarization in Pb(Zr1-xTix)O3 (x = 0.00-0.05) solid solutions was measured for various values of hydrostatic pressure. It was confirmed that the transient ferroelectric phase vanishes for p > pc . The value of pc depends on Ti concentration in the solid solution. From the linear pressure dependences of the phase transition temperatures between P F and F A phases the values of the derivatives dTPF /dp and dTFA dp were determined, respectively. The influence of hydrostatic pressure on the thermodynamic stability of the A, F and P phases was considered from the point of view of the thermodynamic theory of phase transitions.