Character Of Transition Research Articles

Orbital character of the spin-reorientation transition in TbMn6Sn6

Ferromagnetic (FM) order in a two-dimensional kagome layer is predicted to generate a topological Chern insulator without an applied magnetic field. The Chern gap is largest when spin moments point perpendicular to the kagome layer, enabling the capability to switch topological transport properties, such as the quantum anomalous Hall effect, by controlling the spin orientation. In TbMn6Sn6, the uniaxial magnetic anisotropy of the Tb3+ ion is effective at generating the Chern state within the FM Mn kagome layers while a spin-reorientation (SR) transition to easy-plane order above TSR = 310 K provides a mechanism for switching. Here, we use inelastic neutron scattering to provide key insights into the fundamental nature of the SR transition. The observation of two Tb excitations, which are split by the magnetic anisotropy energy, indicates an effective two-state orbital character for the Tb ion, with a uniaxial ground state and an isotropic excited state. The simultaneous observation of both modes below TSR confirms that orbital fluctuations are slow on magnetic and electronic time scales < ps and act as a spatially-random orbital alloy. A thermally-driven critical concentration of isotropic Tb ions triggers the SR transition.

Synergistic effects of Zn B-site substitution in lead-free Ba0.95Ca0.05Ti0.92Sn0.08O3 ferroelectric ceramics for enhancing piezoelectric properties in energy harvesting applications

In this study, lead-free (Ba0.95Ca0.05)(Ti0.92Sn0.08)O3 (BCTS) and (Ba0.95Ca0.05)(Ti0.912Sn0.08Zn0.008)O3 (BCTS-Zn) ceramics with large piezoelectric properties were prepared via the conventional solid-state reaction. The effect of Zn B-site substitution on the structural, dielectric, ferroelectric, energy storage, electrocaloric and piezoelectric properties of BCTS ceramics were systematically investigated. X ray diffraction analysis and Raman spectroscopy of BCTS and BCTS-Zn ceramics confirm the formation of pure phase structure with the coexistence of orthorhombic, tetragonal and pseudo cubic phases at room temperature. The introduction of Zn into BCTS lattice resulted in a denser microstructure with larger average grain size which contributed in the enhancement of the dielectric constant maximum by ⁓35%. Furthermore, the substitution of Ti4+ with a small amount of Zn2+ (0.008) induced a shift in TR-O, TO-T and TT-C transitions towards higher temperatures in addition to an increase in the diffused phase transition character. Moreover, with Zn substitution, an amelioration in the maximum energy storage efficiency is observed from ⁓83% in BCTS ceramic to ⁓88% in BCTS-Zn ceramic. The electrocaloric properties were investigated using the direct and indirect methods. The highest value of the electrocaloric temperature change ΔT = 0.361 K at 319 K was calculated for BCTS ceramic using Maxwell approach with a relatively low electric field of 17.55 kV/cm. For BCTS-Zn ceramic, the enhancement of the piezoelectric properties (d33 = 420 pC/N, g33 = 23.02 mV/mN, FoM = 9.66 pm2/N) is attributed to the synergistic effect of the (O-PC-T) multiphase coexistence, large average grain size and high density of the ceramic. This study reveals that B site Zn substitution in BCTS lattice is an effective approach to improve the piezoelectric properties of the ceramic for energy harvesting applications.

Tunable polarization-drived superior energy storage performance in PbZrO 3 thin films

Antiferroelectric PbZrO₃ films have great potential to be used as the energy storage dielectrics due to the unique electric field-induced phase transition character. But the phase transition process always accompanies polarization hysteresis effect that induces large energy loss and lowers the breakdown strength, leading to inferior energy storage density as well as low efficiency. In this work, the synergistical strategies by doping smaller ions of Li⁺-Al³⁺ to substitute Pb²⁺ and lowering the annealing temperature from 700℃ to 550℃ are proposed to change the microstructure and tune the polarization character of PbZrO₃ films, excepting to dramatically improve the energy storage performances. The prepared Pb_(1-x)(Li_0.5Al_0.5)_xZrO₃(abbreviated as P_(1-x)(L_0.5A_0.5)_xZO) films exhibit ferroelectric-like (<em>FE</em>) rather than antiferroelectric (<em>AFE</em>) character once the doping content of Li⁺-Al³⁺ ions reaches 6 mol%, accompanying a significant improvement of energy storage density of 49.09 J/cm³,but energy storage efficiency is only 47.94% due to the long-correlation of ferroelectric domains. Accordingly, the low-temperature annealing is carried out to reduce the crystalline degree and the polarization loss. P_0.94(L_0.5A_0.5)_0.06ZO films annealed at 550℃ deliver a linear-like polarization rather than ferroelectric-like behavior annealed at 700℃, the lowered remanent polarization as well as improved breakdown strength (4814 kV/cm) result in the superior energy storage density of 58.7 J/cm³ and efficiency of 79.16%, simultaneously possessing excellent frequency and temperature stability, and good electric fatigue tolerance.

Socio-Technical Energy Systems: Configurations That Work Better for Some

The political character of the energy transition requires a fine-grained perspective on the power games occurring to bring it about. There are approaches specifically geared towards calling out the identity-based inequalities in such social processes termed as grand challenges, and then there are those specialised in studying the role of technology in the energy system and how actors in that system interact with these technologies. Feminist social scientists have highlighted the entanglements of intersectionality with technology in general and energy more specifically. At the same time, the literature on Science and Technology Studies (STS) emphasizes a social dimension, e.g., how technology is co-constructed by societal actors or how large technical systems structure our daily lives. Of relevance for feminist social scientists, STS approaches are well-positioned to analyse how technology creates, re-enacts, or mirrors power asymmetries. STS approaches understand technologies as socio-technical systems that inadvertently incorporate societal realities in production and consumption which allows an analysis of the covert seats of power in socio-technical systems. Similarly, energy systems have been a popular research object in STS due to their large-scale, often high-tech character, especially when considering modern energy technologies. Regardless of the common scope of intersectionality and STS regarding power asymmetries, there is still significant room for “hybridization” of these approaches. Although the energy domain has seen efforts being made with the development of notions such as energy poverty, energy justice, or energy democracy, the hybridization effort with STS has not been taken further significantly. This paper, we contributes to the hybridization of the STS and intersectionality lenses.

Beyond Autonomy in Eighteenth-Century British and German Aesthetics

The eighteenth century is a nuisance. At least to the historian bent on coming up with tenable general assertions, or, even worse, encompassing narratives. The richness of eighteenth-century thought is intimidating; its ambiguities are nothing less than baffling. No grand narrative is safe from them, especially the ones that treat the eighteenth century only as an overture of what came afterwards, while ignoring its transitional character, famously described by Koselleck’s term, ‘Sattelzeit’. The eighteenth century was, indeed, the formative period of many of our key concepts; this means, however, that these were still in the making, not yet congealed into their modern forms.1 Unsurprisingly, the eighteenth-century initiation of the discipline named aesthetica, and its antecedents in Europe, have come to be interlocked with the rise of modernity as well. The emergence of aesthetics has been interpreted as a symptom of the entrance of a new image of man, individuality, a modern conception of subjectivity, a new mode of experience, as well as a new ideology or the modern concept of (fine) art into European consciousness. And even though these narratives all situate aesthetics within heteronomous contexts—from physiology and psychology to morality and politics, from social and economic history to belief and religion—one narrative came out as victorious, which neglects the eighteenth-century interpenetration of various disciplines. It offers instead a teleological history of aesthetics which leads towards the concept of autonomy, aesthetic and/or artistic, as it takes shape, allegedly, in the aesthetics of Kant and then Romanticism. The new volume of the Routledge Studies in Eighteenth-Century Philosophy, entitled Beyond Autonomy in Eighteenth-Century British and German Aesthetics, joins the growing body of scholarship that re-examines the influential narratives of autonomy.

Magnetic properties and magnetocaloric effect (MCE) in the melt-spun Tm20Ho20Gd20Ni20Al20 amorphous ribbon

We fabricated the Tm20Ho20Gd20Ni20Al20 ribbons by melt-spun technology and determined its glass forming ability (GFA), magnetic properties, magnetic phase transition (MPT) character, and magnetocaloric performance. The Tm20Ho20Gd20Ni20Al20 melt-spun ribbon exhibits fully amorphous nature and excellent GFA. A second order (SO) type MPT from ferromagnetic to paramagnetic was observed around the Curie temperature of 30.3 K. Moreover, considerable MCE and magnetocaloric performance in Tm20Ho20Gd20Ni20Al20 amorphous ribbon were realized with the maximum magnetic entropy change, temperature-averaged entropy change of 10 K lift, and relative cooling powder/refrigerant capacity of 9.4 J/kgK, 9.0 J/kgK, and 527.2/422.1 J/kg under 0–5 T field change, respectively. These magnetocaloric parameters are close to most of the recently reported magnetocaloric materials, which made the Tm20Ho20Gd20Ni20Al20 amorphous HE ribbon amorphous ribbon also of potential for practical cryogenic MR applications.

Groundwater Urban Heat Island in Wrocław, Poland

In the face of climate change and constantly progressing urbanization processes, so-called heat islands are observed with growing frequency. These phenomena are mainly characteristic of large cities, where increased air and land surface temperatures form an atmospheric (AUHI) or surface (SUHI) urban heat island (UHI). Moreover, UHIs have also been recognized in the underground environments of many cities worldwide, including groundwater (GUHI). However, this phenomenon is not yet as thoroughly studied as AUHI and SUHI. To recognize and characterize the thermal conditions beneath the city of Wrocław (SW, Poland), we analyze the groundwater temperature (GWT) of the first aquifer, measured in 64 wells in 2004–2005. The study aimed to identify groundwater urban heat islands (GUHI) in Wrocław. Therefore, we used a novel approach to gather data and analyze them in predefined seasonal periods. Meteorological data and satellite imagery from the same period allowed us to link GWT anomalies to the typical conditions that favor UHI formation. GWT anomaly related to the GUHI was identified in the central, urbanized part of Wrocław. Moreover, we found that the GUHI phenomenon occurs only seasonally during the winter, which is related to the city’s climate zone and anthropogenic heat sources. Comparing our results with previous works from other cities showed untypical behavior of the observed anomalies. In contrast to AUHI and SUHI temperatures, the GWT anomalies detected in Wrocław are characterized by seasonal transitions from a heat island in winter to a cold lake in summer. Such a transitional character of GUHI is described for the first time.

Phase Transition and Dynamics of Defects in the Molecular Piezoelectric TMCM-MnCl3 and the Effect of Partial Substitutions of Mn

We present dielectric and anelastic spectroscopy measurements of the molecular piezoelectric TMCM-MnCl3 and TMCM-Mn0.95M0.05Cl3 (M = Cu, Fe, Ni; TMCM = trimethylchlorometylammonium), whose powders were pressed into discs and bars and deposited as films on Si by Matrix-Assisted Pulsed Laser Evaporation (MAPLE). As in other molecular ferroelectrics, the dielectric permittivity ϵ′ drops at the structural transition temperature TC, below which the number of directions that the polar TMCM molecules visit is reduced, with the formation of ferroelectric domains. Concomitantly, the Young’s modulus E starts increasing and the elastic energy loss has a step-like increase, attributable to the motion of the domain walls. Both the dielectric and elastic anomalies indicate the improper character of the ferroelectric transition, where the ordering of the molecular orientations is not driven by the cooperative interaction of their electric dipoles. Below room temperature, at least two thermally activated relaxation processes appear both in the dielectric and anelastic spectra, whose real and imaginary parts measured at several frequencies can be fit with the Havriliak–Negami formula. The microscopic parameters so-obtained indicate that they are due to point defects, and it is argued that they are Cl vacancies and their complexes with TMCM vacancies. The considerable width of these relaxation maxima is explained by the geometry of the hexagonal perovskite structure. The partial substitution of Mn with 5% Ni has little effect on the anelastic and dielectric spectra, while Cu and, especially, Fe cause a large enhancement of the losses attributed to domain wall relaxation, with substantial contributions also above TC. The condensation of water from the humidity in the powders compacted by cold pressing was observed and discussed. The piezoelectric activity of the films was assessed by PFM.

Phase transitions in the Haldane-Hubbard model with ionic potentials

By employing the exact-diagonalization method, we revisit the ground-state phase diagram of the Haldane-Hubbard model on the honeycomb lattice with staggered sublattice potentials. The phase diagram includes the band insulator, Mott insulator, and two Chern insulator phases with Chern numbers C=2 and C=1, respectively. The character of transitions between different phases is studied by analyzing the lower-lying energy levels, excitation gaps, structure factors, and fidelity metric. We find that the C=1 phase can be continuously deformed into the C=2 phase without a gap closure in the periodic boundary condition, while a further analysis on the Berry curvatures indicates that the excitation gap closes at the phase boundary in a twisted boundary condition, accompanied by the discontinuities of structure factors. All the other phase transitions are found to be first-order ones as expected.

Heterogeneous Nucleation in Finite-Size Adaptive Dynamical Networks

Phase transitions in equilibrium and nonequilibrium systems play a major role in the natural sciences. In dynamical networks, phase transitions organize qualitative changes in the collective behavior of coupled dynamical units. Adaptive dynamical networks feature a connectivity structure that changes over time, coevolving with the nodes' dynamical state. In this Letter, we show the emergence of two distinct first-order nonequilibrium phase transitions in a finite-size adaptive network of heterogeneous phase oscillators. Depending on the nature of defects in the internal frequency distribution, we observe either an abrupt single-step transition to full synchronization or a more gradual multistep transition. This observation has a striking resemblance to heterogeneous nucleation. We develop a mean-field approach to study the interplay between adaptivity and nodal heterogeneity and describe the dynamics of multicluster states and their role in determining the character of the phase transition. Our work provides a theoretical framework for studying the interplay between adaptivity and nodal heterogeneity.

Autonomy, Constitutivity, Exemplars, Paradigms

This paper proposes an exploration of relationships and exchanges between the philosophies of Cavell and Kuhn by the study of aspects of the philosophy of Wittgenstein. Although the notions of language games and family resemblances used by Kuhn in The Structure of Scientific Revolutions have been elaborated by Wittgenstein, Cavell’s reading of Wittgenstein inspired that of Kuhn. I will attempt to show that against this background, Cavell’s conception of the relations of arts, works of arts, and artists, can be relevantly compared to Kuhn’s conception of the relations of sciences, scientific successes, and scientific practitioners. Three ways of elucidating the mutual exchanges between Cavell and Kuhn may be distinguished: One consists in clarifying the ways in which Cavell and Kuhn explicitly mutually inspired each other. Another one consists in clarifying that Cavell’s Wittgenstein inspired Kuhn. And a third one consists in clarifying that Wittgenstein inspired both Kuhn and Cavell and the ways in which he inspired them. This third way is not exclusive of the first two and even contributes to these by rendering explicit their stakes. For at stake is not only the restitution of the truth of an exegetical mediation: that Kuhn’s Wittgenstein cannot be truly understood without accounting for Cavell’s Wittgenstein. Rather the transitive character of the mediation implied by interpretation does not substitute for the intransitive character of a thoroughly philosophical inheritance. It is not the case that because Kuhn was inspired by Cavell who was inspired by Wittgenstein, that Kuhn could be inspired only by Cavell’s Wittgenstein, and not by Wittgenstein. Further, the question is not only philological but philosophical if we take into account the methods and the philosophy of Wittgenstein. To use an image: that a path was indicated by someone to someone else could not have implied that what was indicated by a person to another was oneself; this much was already known to us with the old fable of the moon, the finger and the sage. With this paper I will thus first seek to establish the relevance of the comparison of Cavell’s conception of the relations of arts, works of arts, and artists with Kuhn’s conception of the relations of sciences, scientific successes, and scientific practitioners. Then I will attempt to render explicit the unrestrictive limits of this comparison both to account for the mutual exchanges between Cavell and Kuhn and consider or bring out some symmetries and asymmetries concerning the place of paradigms in sciences and arts.

Intramolecular Cyclization: A Convenient Strategy to Realize Efficient BT.2020 Blue Multi-Resonance Emitter for Organic Light-Emitting Diodes.

Rationally tuning the emission position and narrowing the full width at half-maximum (FWHM) of an emitter is of great importance for many applications. By synergistically improving rigidity, strengthening the resonant strength, inhibiting molecular bending and rocking, and destabilizing the HOMO energy level, a deep-blue emitter (CZ2CO) with a peak wavelength of 440 nm and an ultranarrow spectral FWHM of 16 nm (0.10 eV) was developed via intramolecular cyclization in a carbonyl/N resonant core (QAO). The dominant υ0-0 transition character of CZ2CO gives a Commission Internationale de I'Éclairage coordinates (CIE) of (0.144, 0.042), nicely complying with the BT.2020 standard. Moreover, a hyper-fluorescent device based on CZ2CO shows a high maximum external quantum efficiency (EQEmax ) of 25.6 % and maintains an EQE of 22.4 % at a practical brightness of 1000 cd m-2 .

Intramolecular Cyclization: A Convenient Strategy to Realize Efficient BT.2020 Blue Multi‐Resonance Emitter for Organic Light‐Emitting Diodes

AbstractRationally tuning the emission position and narrowing the full width at half‐maximum (FWHM) of an emitter is of great importance for many applications. By synergistically improving rigidity, strengthening the resonant strength, inhibiting molecular bending and rocking, and destabilizing the HOMO energy level, a deep‐blue emitter (CZ2CO) with a peak wavelength of 440 nm and an ultranarrow spectral FWHM of 16 nm (0.10 eV) was developed via intramolecular cyclization in a carbonyl/N resonant core (QAO). The dominant υ0‐0transition character of CZ2CO gives a Commission Internationale de I’Éclairage coordinates (CIE) of (0.144, 0.042), nicely complying with the BT.2020 standard. Moreover, a hyper‐fluorescent device based on CZ2CO shows a high maximum external quantum efficiency (EQEmax) of 25.6 % and maintains an EQE of 22.4 % at a practical brightness of 1000 cd m−2.

НАСЕЛЕНИЕ МОРСКИХ ПТИЦ НА ТРАЛОВОМ ПРОМЫСЛЕ МИНТАЯ В ТИХООКЕАНСКИХ ВОДАХ КАМЧАТКИИ СЕВЕРНЫХ КУРИЛЬСКИХ ОСТРОВОВ В ПОЗДНЕОСЕННИЙ ПЕРИОД

The research was carried out in October – December 2022 in the Pacific waters of Kamchatka and the Northern Kuril Islands on aboard medium-tonnage trawler fishing for pollock. We counted seabirds on line transects and in near-vessel aggregations. A total of 28 species were recorded, mainly larids and alcids. The density of bird distribution in the surveyed seawater area was 25.8 birds/km2 on average. Among them alcids (58.6%) and procellariids (27.4%) predominated. Most of the tubenoses and larids (15 species) wandering in the fishing areas were concentrated near the trawler, where they fed on catch processing waste. The most abundant were the northern fulmar and short-tailed shearwater, whose numbers reached 20 and 5 thousand individuals, respectively. The size of the near-vessel aggregations varied significantly during the fishing period. The population of seabirds had a transitional character, as it consisted of resident species that still continued to stay in the nesting areas, as well as transiting and arriving here for the winter from other regions.

Patterns of formation of electrically conductive properties of oxides of the Magneli series

The hybridization of vanadium ions and oxygen ions is considered for four vanadium oxides included in the Magneli series: VO, V 2 O 3 , VO 2 , V 2 O 5 . Based on the data on hybridization, the details of the structure of the crystal lattice of these oxides are analyzed. For each oxide, the role of electrons not participating in the stabilization of the crystal frame in the process of the semiconductor-metal phase transition was revealed. The complex Mott-Peierls character of the phase transitions in all the listed strongly correlated compounds has been established. It is shown that as the degree of oxidation of the V atom increases, the numerical value of the metallic conductivity of the high-temperature phase naturally decreases and, simultaneously, the temperature of the phase transition from the semiconductor to the metallic state increases. Keywords: phase transitions, Magneli series, electron correlations, hybridization of atomic orbitals.

Nonlinear background corrections to dielectric permittivity of ferroics and multiferroics

Temperature measurements of dielectric permittivity are performed for nonstoichiometric ferroelectric lead germanate Pb4.95Ge3O11 and multiferroic solid solution [N(C2H5)4]2CoClBr3. Unlike the heat capacity data, the analysis of the dielectric permittivity of ferroics is usually performed at the assumption that the dielectric `background' is negligible compared with its critical part. In this work we quantitatively interpret the dielectric properties of the single crystals mentioned above and the appropriate literature data for multiferroic Sr2IrO4 crystals, using generalized Curie-Weiss formulas that combine corrections due to a nonlinear temperature-dependent dielectric background, a modified critical index of electric susceptibility, and a diffuse character of phase transition. We argue that taking account of the temperature dependent dielectric background can improve notably the quantitative analysis of PTs for a number of classes of the ferroic materials.

Закономерности формирования электропроводящих свойств окислов ряда Магнели

The hybridization of vanadium ions and oxygen ions is considered for four vanadium oxides included in the Magneli series: VO, V2O3, VO2, V2O5. Based on the data on hybridization, the details of the structure of the crystal lattice of these oxides are analyzed. For each oxide, the role of electrons not participating in the stabilization of the crystal frame in the process of the semiconductor-metal phase transition was revealed. The complex Mott-Peierls character of the phase transitions in all the listed strongly correlated compounds has been established. It is shown that as the degree of oxidation of the V atom increases, the numerical value of the metallic conductivity of the high-temperature phase naturally decreases and, simultaneously, the temperature of the phase transition from the semiconductor to the metallic state increases. Keywords: phase transitions, Magneli series, electron correlations, hybridization of atomic orbitals.

Electrochemically-Switched 2nd Order Non-Linear Optical Response in an Arylimido-Polyoxometalate with High Contrast and Cyclability.

Electrochemically switched 2nd order non-linear optical responses have been demonstrated for the first time in polyoxometalates (POMs), with an arylimido-derivative showing a leading combination of high on/off contrast (94 %), high visible transparency, and cyclability. Spectro-electrochemical and TD-DFT studies indicate that the switch-off results from weakened charge transfer (CT) character of the electronic transitions in the reduced state. This represents the first study of an imido-POM reduced state, and demonstrates the potential of POM hybrids as electrochemically activated molecular switches.

Electrochemically‐Switched 2nd Order Non‐Linear Optical Response in an Arylimido‐Polyoxometalate with High Contrast and Cyclability

AbstractElectrochemically switched 2nd order non‐linear optical responses have been demonstrated for the first time in polyoxometalates (POMs), with an arylimido‐derivative showing a leading combination of high on/off contrast (94 %), high visible transparency, and cyclability. Spectro‐electrochemical and TD‐DFT studies indicate that the switch‐off results from weakened charge transfer (CT) character of the electronic transitions in the reduced state. This represents the first study of an imido‐POM reduced state, and demonstrates the potential of POM hybrids as electrochemically activated molecular switches.

Coherent control of the photoinduced transition in a strongly correlated material

The use of intense tailored light fields is the perfect tool to achieve ultrafast control of electronic properties in quantum materials. Among them, Mott insulators are materials in which strong electron-electron interactions drive the material into an insulating phase. When shining a Mott insulator with a strong laser pulse, the electric field may induce the creation of doublon-hole pairs, triggering a photoinduced transition into a metallic state. In this paper, we take advantage of the threshold character of this photoinduced transition and we propose a setup that consists of a midinfrared laser pulse and a train of short pulses separated by a half period of the midinfrared with alternating phases. By varying the time delay between the two pulses and the internal carrier envelope phase of the short pulses, we achieve control of the phase transition, which leaves its fingerprint at its high harmonic spectrum.