First-order Phase Transition Temperature Research Articles

Structures and velocities of noisy ferroelectric domain walls

Ferroelectric domain wall motion is fundamental to the switching properties of ferroelectric devices and is influenced by a wide range of factors including spatial disorder within the material and thermal noise. We build a Landau-Ginzburg-Devonshire (LGD) model of ${180}^{\ensuremath{\circ}}$ ferroelectric domain wall motion that explicitly takes into account the presence of both spatial disorder and thermal noise. We demonstrate both creep flow and linear flow regimes of the domain wall dynamics by solving the LGD equations in a Galilean frame moving with the wall velocity $v$. Thermal noise plays a key role in the wall depinning process at small fields $E$. We study the scaling of the velocity $v$ with the applied DC electric field $E$ and show that noise and spatial disorder strongly affect domain wall velocities. We also show that domain walls develop a local, metastable paraelectric region and widen significantly in the presence of thermal noise in materials with ``multiwell'' potentials, representative of ferroelectrics at temperatures $T$ just below a first-order phase transition (Curie) temperature ${T}_{c}$. These calculations point to the potential of noise and disorder to become control factors for the switching properties of ferroelectric materials, for example for advancement of microelectronic applications.

Leptogenesis triggered by a first-order phase transition

We propose a new scenario of leptogenesis, which is triggered by a first-order phase transition (FOPT). The right-handed neutrinos (RHNs) are massless in the old vacuum, while they acquire a mass in the new vacuum bubbles, and the mass gap is huge compared with the FOPT temperature. The ultra-relativistic bubble walls sweep the RHNs into the bubbles, where the RHNs experience fast decay and generate the lepton asymmetry, which is further converted to the baryon asymmetry of the Universe (BAU). Since the RHNs are out of equilibrium inside the bubble, the generated BAU does not suffer from the thermal bath washout. We first discuss the general feature of such a FOPT leptogenesis mechanism, and then realize it in an extended B − L model. The gravitational waves from U(1)B−L breaking could be detected at the future interferometers.

Correlation between magnetic and crystal structural sublattices in palladium-doped FeRh alloys: Analysis of the metamagnetic phase transition driving forces

FeRh alloys doped with the third element exhibit a change in the lattice and magnetic subsystems, which are manifested in antiferromagnetic- ferromagnetic (AFM-FM) first-order phase transition temperature, the shrinkage of the temperate hysteresis under transition, and the reduction of the saturation magnetization. All aforementioned parameters are crucial for practical applications. To control them it is quite important to determine the driving forces of the metamagnetic transition and its origins. In this manuscript ab initio calculations and experimental studies results are presented, which demonstrate the correlation between the structural and magnetic properties of the Fe50Rh50−xPdx alloys. The qualitative analysis of the metamagnetic phase transition driving forces in palladium-doped FeRh alloys was performed to determine their contribution to the evolution of magnetic and lattice subsystems. In addition, the impact of the impurities phases together with its magnetic behavior on the AFM-FM phase transition was considered.

Calculation of the Relaxation Time and the Activation Energy Close to the Lower Phase Transition in Imidazolium Perchlorate

The temperature dependence of the relaxation time of imidazolium perchlorate (Im-ClO4) was calculated from the pseudospin-phonon coupled (PS) and the energy fluctuation (EF) models close to the first-order phase transition temperature of 247 K. This calculation was performed in terms of the proton second moment M2 that was associated with the order parameter which was predicted from the mean-field theory. Our results were in good agreement with the observed data. In addition, values of the activation energy were deduced in terms of the Arrhenius plot using our calculated values of the relaxation time from both PS and EF models.

Latent heat and pressure gap at the first-order deconfining phase transition of SU(3) Yang–Mills theory using the small flow-time expansion method

Abstract We study latent heat and the pressure gap between the hot and cold phases at the first-order deconfining phase transition temperature of the SU(3) Yang–Mills theory. Performing simulations on lattices with various spatial volumes and lattice spacings, we calculate the gaps of the energy density and pressure using the small flow-time expansion (SF$t$X) method. We find that the latent heat $\Delta \epsilon$ in the continuum limit is $\Delta \epsilon /T^4 = 1.117 \pm 0.040$ for the aspect ratio $N_s/N_t=8$ and $1.349 \pm 0.038$ for $N_s/N_t=6$ at the transition temperature $T=T_c$. We also confirm that the pressure gap is consistent with zero, as expected from the dynamical balance of two phases at $T_c$. From hysteresis curves of the energy density near $T_c$, we show that the energy density in the (metastable) deconfined phase is sensitive to the spatial volume, while that in the confined phase is insensitive. Furthermore, we examine the effect of alternative procedures in the SF$t$X method—the order of the continuum and the vanishing flow-time extrapolations, and also the renormalization scale and higher-order corrections in the matching coefficients. We confirm that the final results are all very consistent with each other for these alternatives.

Design and development of innovative microparticulate/nanoparticulate inhalable dry powders of a novel synthetic trifluorinated chalcone derivative and Nrf2 agonist

Chalcone derivatives are shown to possess excellent anti-inflammatory and anti-oxidant properties which are of great interest in treating respiratory diseases such as acute lung injury (ALI), acute respiratory distress syndrome (ARDS), chronic obstructive pulmonary disease (COPD), and pulmonary fibrosis (PF). This study successfully designed and developed dry powder inhaler (DPI) formulations of TMC (2-trifluoromethyl-2′-methoxychalone), a new synthetic trifluorinated chalcone and Nrf2 agonist, for targeted pulmonary inhalation aerosol drug delivery. An advanced co-spray drying particle engineering technique was used to design and produce microparticulate/nanoparticulate formulations of TMC with a suitable excipient (mannitol) as inhalable particles with tailored particle properties for inhalation. Raw TMC and co-spray dried TMC formulations were comprehensively characterized for the first time using scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) spectroscopy, thermal analysis, X-ray powder diffraction (XRPD), and molecular fingerprinting as dry powders by ATR-FTIR spectroscopy and Raman spectroscopy. Further, biocompatibility and suitability of formulations were tested with in vitro cellular transepithelial electrical resistance (TEER) in air-interface culture (AIC) using a human pulmonary airway cell line. The ability of these TMC formulations to perform as aerosolized dry powders was systematically evaluated by design of experiments (DOEs) using three different FDA-approved human inhaler devices followed by interaction parameter analyses. Multiple spray drying pump rates (25%, 75%, and 100%) successfully produced co-spray dried TMC:mannitol powders. Raw TMC exhibited a first-order phase transition temperature at 58.15 ± 0.38 °C. Furthermore, the results demonstrate that these innovative TMC dry powder particles are suitable for targeted delivery to the airways by inhalation.

Quenching induced enhancement of coupling between the molecule reorientation and grain boundary relaxation in polycrystalline C60

Dielectric spectroscopy was performed on polycrystalline C60 powder at selected frequencies from 111 Hz to 2 MHz as the temperature rose from 100 K to 473 K. About 3 K increase of the first-order phase transition temperature caused by quenching was observed, but disappeared in the second heating cycle. The apparent activation energy of dipole relaxation in low temperature range increases to 387 ± 4 meV which is 19 meV higher than that of pristine C60. Meanwhile, a novel grain boundary (GB) relaxation was also found in the quenched C60. It is suggested that quenching increase the GB viscosity, which facilitates the coupling between the GB motion and C60 orientation jump.

Effect of annealing on the magnetic ordering and electron magnetic resonance of melt-spun Ni-Mn-In ribbons

In this study, the electron magnetic resonance (EMR) spectra of annealed Ni50Mn35.5In14.5 Heusler alloy ribbons within the temperature range 240 K⩽T⩽360 K are investigated. In the paramagnetic region, the temperature dependence of the EMR linewidth is governed by the Korringa relaxation process. The g value exhibits a positive shift, which indicates a non-bottleneck regime. The temperature dependence of inverse integrated intensity exhibits a Curie-Weiss like behaviour with TC equals 298 K. The effects of annealing on the magnetic and structural ordering are discussed. Annealing increases the Curie temperature and changes the first-order phase transition temperature. Additionally, the low-field microwave absorption peak appears below the magnetic ordering temperature.

Isothermal Entropy Change for the Spin-1 Blume-Capel Model on the Bethe Lattice

The isothermal entropy change of spin-1 Blume-Capel (BC) is investigated on the Bethe lattice (BL) with the variations of coordination numbers (q), crystal field (D) and external magnetic field (H) in the vicinity of critical temperatures, i.e. about the second- and first-order phase transition temperatures. The calculation is carried on the BL in terms of exact recursion relations. It is found that the peaks of the isothermal entropy variation obtained for both magnetization and quadrupole moments are observed to be increasing with increasing values of H for given D and q, decreasing with the increasing q for fixed D and H and also decreasing with the increasing values of D for constant q and H. The peaks of the curves for the quadrupole moment is less sharper then the ones obtained for the magnetization.

The influence of combination of the first-order and second-order phase transitions on magnetocaloric effects in Mn3Cu1-xFexN

The influences of Fe substitutions on magnetic properties, phase transformations and magnetocaloric effects of Mn3Cu1-xFexN have been investigated. The magnetic phase transition temperature (Tc) increases but the first-order phase transition temperature decreases with increasing the Fe content. Fe doping separates the first-order phase transition into first-order and second-order phase transitions in Mn3Cu1-xFexN. The second-order (paramagnetic-ferromagnetic) transition coexists with first-order (ferromagnetic-ferrimagnetic) transition in Mn3Cu0.95Fe0.05N. Introduction of the second-order magnetic transition broadens the phase transition span, which greatly enhances the relative cooling power of Mn3CuN. The results indicate that resolving complex magnetic phase transition may improve the cooling capacity of antiperovskite compounds.

Frequency Switches at Transition Temperature in Voltage-Gated Ion Channel Dynamics of Neural Oscillators**Supported by JST, CREST, and JSPS KAKENHI under Grant No 15H05919.

Understanding of the mechanisms of neural phase transitions is crucial for clarifying cognitive processes in the brain. We investigate a neural oscillator that undergoes different bifurcation transitions from the big saddle homoclinic orbit type to the saddle node on an invariant circle type, and the saddle node on an invariant circle type to the small saddle homoclinic orbit type. The bifurcation transitions are accompanied by an increase in thermodynamic temperature that affects the voltage-gated ion channel in the neural oscillator. We show that nonlinear and thermodynamical mechanisms are responsible for different switches of the frequency in the neural oscillator. We report a dynamical role of the phase response curve in switches of the frequency, in terms of slopes of frequency-temperature curve at each bifurcation transition. Adopting the transition state theory of voltage-gated ion channel dynamics, we confirm that switches of the frequency occur in the first-order phase transition temperature states and exhibit different features of their potential energy derivatives in the ion channel. Each bifurcation transition also creates a discontinuity in the Arrhenius plot used to compute the time constant of the ion channel.

The crystal-field dependency of sound attenuation in the spin-3/2 ising model

The effects of crystal-field (D) on sound attenuation are considered for the spin-3/2 Ising model by using Onsager theory of irreversible thermodynamics. It is assumed that the sound wave couples to the order-parameter fluctuations, therefore, it decays mainly via order-parameter relaxation process. The order-parameters, magnetization and quadrupole moment, are defined in terms of exact recursion relations (ERR) on Bethe lattice (BL). After our analysis, two relaxation times are obtained and they are used to calculate the sound attenuation coefficient (α). Consequently, the critical behaviors of sound attenuation coefficient are investigated in terms of frequency (w) and Onsager coefficient (γ) for the coordination numbers q=3, 4 ad 6 near the second-order (Tc) and first-order (Tt) phase transition temperatures in the ferromagnetic phase regions for the negative and positive D values and the results are presented on the (kBT/J, α) planes. It is found that the peaks about Tt’s are observed at the same temperature, but the peaks about Tc’s are observed shifted to lower and higher temperatures in increasing (w)’s and (γ)’s, respectively. In addition, the peaks are also obtained near the tricritical points for all q.

Vibrational properties of anhydrous and partially hydrated uranyl fluoride.

Uranyl fluoride (UO2F2) is a hygroscopic powder with two main structural phases: an anhydrous crystal and a partially hydrated crystal of the same R3¯m symmetry. The formally closed-shell electron structure of anhydrous UO2F2 is amenable to density functional theory calculations. We use density functional perturbation theory (DFPT) to calculate the vibrational frequencies of the anhydrous crystal structure and employ complementary inelastic neutron scattering and temperature-dependent Raman scattering to validate those frequencies. As a model closed-shell actinide, we investigated the effect of LDA, GGA, and non-local vdW functionals as well as the spherically averaged Hubbard +U correction on vibrational frequencies, electronic structure, and geometry of anhydrous UO2F2. A particular choice of Ueff=5.5 eV yields the correct U-Oyl bond distance and vibrational frequencies for the characteristic Eg and A1g modes that are within the resolution of experiment. Inelastic neutron scattering and Raman scattering suggest a degree of water coupling to the lattice vibrations in the more experimentally accessible partially hydrated UO2F2 system, with the symmetric stretching vibration shifted approximately 47 cm-1 lower in energy compared to the anhydrous structure. Evidence of water interaction with the uranyl ion is present from a two-peak decomposition of the uranyl stretching vibration in the Raman spectra and anion-hydrogen stretching vibrations in the inelastic neutron scattering spectra. A first-order dehydration phase transition temperature is definitively identified to be 125 °C using temperature-dependent Raman scattering.

Experimental Observation of a Possible First-Order Phase Transition below the Superconducting Transition Temperature in the Multilayer Cuprate Superconductor HgBa2Ca4Cu5Oy

A first-order phase transition is found in the multilayer cuprate superconductor, HgBa$_2$Ca$_4$Cu$_5$O$_y$ (Hg-1245), with a superconducting transition temperature of 108 K, under zero magnetic field. We observed a hysteretic specific heat jump around 41 K. We conclude that the Bardeen-Cooper-Schrieffer pairs have a residual entropy due to fluctuations in the phase difference between the five CuO$_2$ planes in a unit cell of Hg-1245, and that this fluctuation freezes below the first-order phase transition temperature.

Fine Structure Observation in Magnetostriction Near the First-Order Phase Transition Temperature in Gd$_{5}$Si$_{1.95}$Ge$_{2.05}$

Gd5(SixGe1 - x)4 has a complex magnetic-structural phase diagram which can be divided into three distinct regions. It exhibits an unusual first-order coupled magnetic-structural phase transition in the region x <; 0.51. A series of magnetostrictive strain measurements were carried out as a function of magnetic field strength at different temperatures and as a function of temperature at near-zero magnetic field strengths. In this paper, we report for the first time the observation of fine structure in the variation of strain with magnetic field near the first-order phase transition temperature. This fine structure was observed only for the single-crystalline and polycrystalline samples of Gd5Si1.95Ge2.05 but not for Gd5Si2Ge2 and Gd5Si2.09Ge1.91 samples. There was a sudden increase of about 200-300 ppm in the magnetostrictive strain just prior the field-induced first-order phase transition. In this paper, this anomaly is termed as fine structure. It was observed in measurements of both magnetostrictive strain versus magnetic field and magnetostrictive strain versus temperature. In the case of the polycrystalline Gd5Si1.95Ge2.05 sample, this anomaly was not as sharp, and the sudden magnetostrictive strain change was about 40 ppm just before the field-induced first-order phase transition.

Metastability in the Magnetic Structure of Ni&lt;sub&gt;51&lt;/sub&gt;Mn&lt;sub&gt;33.4&lt;/sub&gt;In&lt;sub&gt;15.6&lt;/sub&gt; Heusler Alloy

The metastability of the nonstoichiometric Ni <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">51</sub> Mn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">33.4</sub> In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15.6</sub> Heusler alloy in the first-order transition region is studied using direct adiabatic temperature change (ΔT <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ad</sub> ) measurements for heating and cooling magnetization processes. During the heating process, ΔT <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ad</sub> shows an unusual pronounced peak at 294 K in low applied magnetic fields. The height of this peak diminishes and eventually vanishes at higher fields. Kinks are as well observed in the 290-295 K temperature interval for both processes. The existence of the peak and kinks is indicative of the complex magnetic dynamics in Ni <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">51</sub> Mn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">33.4</sub> In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15.6</sub> and is attributed to a spin-reorientation transition near the first-order phase transition temperature.

Size dependent transition enthalpy in PbTiO3 nanoparticles due to a cubic surface layer

Size dependence of transition enthalpy observed in ferroelectric PbTiO3 nanoparticles has been shown to result from volume averaging or the surface dilution effect rather than size induced reduction of spontaneous polarization at the first-order phase transition temperature. The PbTiO3 nanoparticles are suggested to be composed of a cubic surface layer with size independent thickness and a ferroelectric core having nonzero and size independent spontaneous polarization at the transition point. Based on a surface layer model, thickness of the cubic surface layer at the Curie temperature is estimated to be around 5–8 nm for PbTiO3 nanoparticles from the literature-reported transition enthalpy data. The present analyses indicate that the size effect in ferroelectrics is possibly a surface related extrinsic effect.

Influence of temperature on the optical properties of zinc tris-thiourea sulfate (ZTS) single crystal

Single crystal of zinc tris-thiourea sulfate (ZTS) was synthesized and grown by the slow evaporation technique at 315K. The effect of temperature on the optical properties of ZTS crystal was studied in the temperature range 293–338K. This range involves the first-order phase transition temperature from ferroelectric to paraelectric phase (323K). At room temperature (293K), the optical transmittance (T) has high values in the completely visible wavelength range. The cut off wavelength equals to 278.5nm at room temperature. By increasing temperature, the optical transmittance decreases, however the cut off shifts to higher wavelengths. These changes have different rates in the two phases (ferroelectric and paraelectric). Analysis reveals that the type of transition is the direct allowed one. The optical energy gap (Eg) has the value of 3.89eV at room temperature. This value decreases linearly with increasing temperature by different rates in the two phases. In the region of the absorption edge, the absorption coefficient obeys Urbach’s rule, and Urbach parameters were calculated. The Urbach tail energy (Ee), which equals to 1.024eV at room temperature, increases linearly with increasing temperature. This change has different rates in the two phases. At room temperature, the steepness parameter (σ) has the value of 24.697×10−3. It decreases linearly with increasing [1/(Temp.)2] by different rates in the two phases. For all studied parameters, the temperature dependence relations change considerably while passing through 323K. This anomalous behavior confirms that the transition from ferroelectric to paraelectric phase occurs at this temperature.

The crystal field effects on sound attenuation for a spin-1 Ising model on the Bethe lattice

The sound attenuation phenomenon is investigated by using the Onsager theory of irreversible thermodynamics for a spin-1 Ising model with the inclusion of the crystal field effects on the Bethe lattice. The recursion relations are calculated in a transcendental form to obtain the order-parameters and then the sound attenuation is analyzed. The relationships of sound attenuation with temperature, frequency and Onsager coefficient are examined near the second- and first-order phase transition temperatures, Tc and Tt respectively, for given negative crystal field values and coordination numbers on the Bethe lattice. The sound wave couples to the order-parameter fluctuations which decay mainly via the order-parameter relaxation process. Thus, two relaxation times are obtained which are used to find an expression for the sound attenuation coefficient. The attenuation maxima are found near the second- and first-order phase transition temperatures in the ferromagnetic and quadrupole phase regions, respectively, for the coordination numbers q = 3,4 and 6. The attenuation peaks are observed at the same temperature before Tt and are found to be shifted to lower (higher) temperatures with increasing value of frequency (Onsager coefficient) before Tc for any crystal field values. The attenuation peaks are found at lower values and at higher temperatures with negatively increasing crystal field values in the quadrupolar phase regions. In addition, the sound attenuation peaks are also studied at some tricritical points for q = 3,4 and 6 for some critical values of the crystal field.

The Bethe lattice treatment of sound attenuation for a spin- 3/2 Ising model

The sound attenuation phenomena is investigated for a spin- 3/2 Ising model on the Bethe lattice in terms of the recursion relations by using the Onsager theory of irreversible thermodynamics. The dependencies of sound attenuation on the temperature (T), frequency (w), Onsager coefficient (γ) and external magnetic field (H) near the second-order (Tc) and first-order (Tt) phase transition temperatures are examined for given coordination numbers q on the Bethe lattice. It is assumed that the sound wave couples to the order-parameter fluctuations which decay mainly via the order-parameter relaxation process, thus two relaxation times are obtained and which are used to obtain an expression for the sound attenuation coefficient (α). Our investigations revealed that only one peak is obtained near Tt and three peaks are found near Tc when the Onsager coefficient is varied at a given constant frequency for q=3. Fixing the Onsager coefficient and varying the frequency always leads to two peaks for q=3,4 and 6 near Tc. The sound attenuation peaks are observed near Tt at lower values of external magnetic field, but as it increases the sound attenuation peaks decrease and eventually disappear.