Width Of Hysteresis Loop Research Articles

Thermo-mechanical response of near-pearlitic steel heated under restriction of thermal expansion

Railway wheels experience high temperatures during operation, especially during severe block braking. The thermal expansion of wheel rim material due to frictional heating is limited by the wheel's geometry and size. This study investigated the impact of this combined mechanical and thermal loading on the mechanical properties and microstructure in the tread surface of an ER7T steel railway wheel.The material response below the austenitisation temperature is comprehensively evaluated through thermal cycling at peak temperatures of 300, 400, 600, and 650 °C, simulating severe block braking cycles with varying degrees of thermal dilatation (25 %, 50 %, 75 %, and 100 %). An initial plastic deformation was observed during the first heating cycle for the two lower temperatures at lower restrictions, followed by a predominantly elastic response. However, at higher restrictions, the material showed time-dependent relaxation during heating, and some plastic deformation was observed during cooling. Notably, even at the lowest level of restriction, similar observations were made at higher peak temperatures. Increasing the restriction resulted in large strains and a wider hysteresis loop. The test bars exposed to the two higher temperatures retained large tensile stresses after cooling. This indicates a risk of a significantly altered residual stress state in the rim of an overheated railway wheel, which could adversely affect its fatigue properties. The study's outcomes will aid in designing and calibrating constitutive material models for severe block braking. Furthermore, it will significantly contribute to research into the thermo-mechanical behaviour of pearlitic/near-pearlitic materials during railway operations and maintenance.

Exploring channel length effects in 2D MoS2-Based memtransistors and their Synaptic behavior

Memtransistors, combining the functionalities of memristors and transistors, signify a substantial advancement with potential applications in areas such as neuromorphic learning and the integration of processing and memory units in current computers. Particularly, memtransistors fabricated using 2D materials have received extensive research attention due to their memory capabilities, energy efficiency, and features enabling compact integration. In this study, we examined the utilization of MoS2 monolayers grown by chemical vapor deposition (CVD), inherently imbued with defects, as memtransistors. Our focus probed into the exploration of how the change in channel length within this imperfect architectural construct exerts influences on the hysteresis loop and hence the operation of the device. In this respect, increasing the gate voltage enhanced the distinction between high and low resistance states and lengthening the channel led to a decrease in the differentiation between resistance states. Despite the shrinkage in hysteresis loop width, the memristive characteristics were preserved even at low gate voltages. Shortening the channel length widened the gap between low and high resistance states but disrupted the loop symmetry. Interestingly, relatively long channel memtransistors exhibited a more symmetrical and closer-to-ideal hysteresis. Experiments in different environments highlighted the impact of photocurrent. We applied consecutive pulses, resulting in an increase in the baseline of the current graph. Short-lived changes in the memtransistors resistance suggested its potential to simulate the short-term potentiation property of synapses. Our study on CVD grown 2D material-based memtransistors provides insights into the potential of using such defected materials in memtransistors wide usage and demonstrating their ability to emulate synaptic behavior.

Characterizing the electric field- and rate-dependent hysteresis of piezoelectric ceramics shear motion with the Bouc-Wen model

Piezoelectric technology is widely used in the field of precision drives. However, when piezoelectric actuators are employed at high voltages and high frequencies, their hysteresis can greatly affect the accuracy of such systems. The Bouc-Wen model has typically been used by researchers to characterise the hysteresis of piezoelectric materials. Besides, to extract the parameters of this model from experimental data, particle swarm optimization (PSO) is often employed. However, the majority of such studies only considers hysteresis as a function of the electric field strength and not as a function of actuation frequency. In addition, most of such existing reports have focused on longitudinal type piezo actuators. In this context, the research presented here complements this body of knowledge by demonstrating the application of the PSO algorithm for determining the parameters of the Bouc-Wen model when hysteresis depends not only on the electric field but also on the rate of the driving signal and when applied on a shear-type piezoelectric actuator. The obtained experimental data showed that with the increase of electric field strength, both the piezoelectric coefficient and hysteresis value increased significantly, and that with the increase of frequency, the piezoelectric coefficient decreased, while the hysteresis value changed slightly. The variations of the Bouc-Wen model parameters with the electric field and frequency were identified and then used to predict the shear motion trajectory of the piezoelectric stack. It was found that in the identified range of electric field and frequency, the predicted error rate of the hysteresis loop amplitude was less than 16.5% with a minimum value of 0.1%, and the error rate of the hysteresis loop width was less than 14.5% with a minimum value of 2.7%. Based on the identified electric field- and rate-dependent Bouc-Wen model, a novel finite element (FE) model was also proposed to analyse the effect of electrical and mechanical coupling on the piezoelectric movement.

Resilience of the Aurivillius structure upon La and Cr doping in a Bi5Ti3FeO15 multiferroic.

Combining the experimental techniques of high-resolution X-ray diffraction, magnetometry, specific heat measurement, and X-ray photoelectron, Raman and dielectric spectroscopy techniques, we have studied the influence of La and Cr doping on the crystal structure and magnetism of the room temperature Aurivillius multiferroic Bi5Ti3FeO15 by investigating the physical properties of (Bi4La)Ti3FeO15 and Bi5Ti3 (Fe0.5Cr0.5)O15. The parent (Bi5Ti3FeO15) and the doped ((Bi4La)Ti3FeO15 and Bi5Ti3(Fe0.5Cr0.5)O15) compounds crystallize in the A21am space group, which is confirmed through our analysis of high-resolution synchrotron X-ray diffraction data obtained on phase-pure polycrystalline powders. We determined the oxidation states of the metal atoms in the studied compounds as Fe3+, Ti4+, Cr3+, and La3+ through the analysis of X-ray photoelectron spectroscopy data. The magnetic susceptibilities of the three compounds are marked by the absence of a long-range ordered ground state, but dominated by superparamagnetic clusters with dominant antiferromagnetic interactions. This signature of short-range magnetism is also seen in specific heat as a low temperature enhancement which is suppressed upon the application of external magnetic fields up to 8 T. Our dielectric spectroscopy experiments showed that the three studied compounds display similar features in the dielectric constant measured as a function of frequency. However, upon doping La at the Bi site, the width of the ferroelectric hysteresis loop increases for (Bi4La)Ti3FeO15 compared to that of the parent compound Bi5Ti3FeO15, and with Cr doping, Bi5Ti3(Fe0.5Cr0.5)O15 becomes a leaky dielectric. The resilience of the Aurivillius crystal structure towards doping of La at the Bi site and Cr at the Fe site is clearly seen in the bulk properties of magnetic susceptibility, specific heat and the average crystal structure. The relevance of changes in the local structure is evident from our Raman spectroscopy and X-ray pair distribution function studies.

The hydrate of a neutral iron(III) complex based on the pyruvic acid thiosemicarbazone ligand with abrupt spin-crossover with T1/2 = 340 K and a wide hysteresis loop of 45 K.

The hydrate of a neutral iron(III) complex based on the pyruvic acid thiosemicarbazone ligand [FeIII(Hthpy)(thpy)]·H2O (1) was synthesized and characterized using FT-IR spectroscopy, powder and single-crystal X-ray diffraction, dc magnetic measurements, EPR and 57Fe Mössbauer spectroscopy. The crystal structure of 1 was determined for the first time. Two distinct chelating ligands Hthpy- and thpy2- coordinate the Fe(III) ion to form the FeN2O2S2 octahedron which shows a low spin geometry at 150-350 K. The crystal packing contains infinite chains of the Fe(III) complexes as well as water molecules located in cavities. Along the chain, π-π interacting pairs of the Fe complexes are linked by H-bonding. According to the dc magnetic measurements, the complete abrupt spin-crossover with half-transition temperature T1/2 = 340 K and a hysteresis loop of 45 K occurs in the temperature range of 300-363 K. Based on the X-ray structure of 1, the Bleaney-Bowers equation for the isolated dimer model was used to approximate the temperature dependence of the magnetic susceptibility in the range of 2-50 K. The defined intradimer exchange constant Jexp = -0.498(1) K corresponds to a weak antiferromagnetic exchange between the iron(III) magnetic centers. DFT calculations of H- and π-π bonded fragments of the crystal structure of 1 in the HS and LS states were carried out. Moreover, BS-DFT calculations confirm the presence of antiferromagnetic exchange Jcalc = -0.92 K in the π-π bonded pairs of the ferric complexes and show the exchange pathway between Fe(III) ions by the calculated spin density distribution.

Ferroelectric relaxor behaviour in Bi and K/Na-substituted solid solutions of tetragonal tungsten bronze PbNb2O6

Lead metaniobate (PbNb2O6 or PNO) belongs to the tetragonal tungsten bronze (TTB) family. There are three polymorphic forms of PNO: tetragonal (stable at high temperature), rhombohedral (stable at room temperature), and the metastable orthorhombic phase, which has ferroelectric properties. The metastable orthorhombic phase is formed by quenching from the high temperature tetragonal phase due to the reconstructive/sluggish tetragonal to rhombohedral phase transition. A suitable ionic substitution can also lead to the stable ferroelectric orthorhombic phase. Stabilization of the ferroelectric orthorhombic phase by ionic substitution, and the formation of ferroelectric relaxors with increased amounts of dopants is hereby reported for the compositions Pb(1-x)Bi(x/2K(x/2)Nb2O6 and Pb(1-x)Bi(x/2)Na(x/2)Nb2O6. The solid solutions of PNO showed evidence of linked dielectric relaxation and ferroelectricity, validating the distinctive ferroelectric relaxor behaviour for the compositions Pb0.6Bi0.2K0.2Nb2O6 and Pb0.6Bi0.2Na0.2Nb2O6. As the concentrations of bismuth (Bi) and potassium/sodium (K/Na) dopants increased, the Curie temperature (Tc), or the temperature corresponding to the maximum dielectric permittivity (Tm), dropped. By using the Uchino-Nomura relation as a modification of the Curie-Weiss law, it was established that the Pb0.6Bi0.2K0.2Nb2O6 solid solution exhibit higher degree of diffuseness than Pb0.6Bi0.2Na0.2Nb2O6 at the transitions. The width of the ferroelectric hysteresis loop increased as the percentage of dopants increased, from x = 0.1 to x = 0.3. At x = 0.4, a narrow ferroelectric hysteresis loop and a frequency-dependent Tm abruptly formed, which is indicative of a ferroelectric relaxor.

CuS/SnS quantum dot-nanorod composites: Ferromagnetic and gigantic dielectric characteristics

In this study, new CuS/SnS nanocomposites were simply synthesized by coprecipitation route for capacitive energy storage applications. The results of the XRD analysis confirmed the formation of hexagonal CuS and orthorhombic α-SnS phases. The TEM images of CuS/SnS (1:1) and CuS/SnS (1:3) composites showed the formation of quantum dot particles (2–3 nm) besides nanorods particles (length 56–80 nm and diameter 9–16 nm). The TEM images of CuS/SnS (3:1) sample illustrated the formation of only quantum dot particles (2–3 nm). Infrared band gap energies of 0.8, 0.95 and 1.25 eV were measured for CuS/SnS (1:1), CuS/SnS (3:1) and CuS/SnS (1:3) composites, respectively. CuS/SnS (1:1) composite has a wide hysteresis loop until magnetic field of ±3500 Oe with magnetization (Ms) and coercivity (Hc) values of 0.009 emu/g and 1000 Oe, respectively. For CuS/SnS (1:3) composite, the hysteresis loop possesses a semi-ferromagnetic shape with measured magnetization value of 0.018 emu/g and Hc of 551 Oe. The ferromagnetic order can be attributed to defects as well as the surface interface interaction between CuS and SnS particles. Remarkably, CuS/SnS composites exhibit a giant dielectric constant (>106) with low temperature dependent, making them promising compositions for capacitive energy storage applications. At room temperature, CuS/SnS (1:1), CuS/SnS (3:1) and CuS/SnS (1:3) composites possess colossal dielectric constant values of ∼2.9 × 106, 5.5 × 105 and 6.3 × 106 at frequency of 42 Hz, respectively.

Symmetry Breaking and Cooperative Spin Crossover in a Hofmann-Type Coordination Polymer Based on Negatively Charged {FeII(μ2-[MII(CN)4])2}n2n- Layers (MII = Pd, Pt).

We report herein the synthesis and characterization of two unprecedented isomorphous spin-crossover two-dimensional coordination polymers of the Hofmann-type formulated {FeII(Hdpyan)2(μ2-[MII(CN)4])2}, with MII = Pd, Pt and Hdpyan is the in situ partially protonated form of 2,5-(dipyridin-4-yl)aniline (dpyan). The FeII is axially coordinated by the pyridine ring attached to the 2-position of the aniline ring, while it is equatorially surrounded by four [MII(CN)4]2- planar groups acting as trans μ2-bidentate ligands defining layers, which stack parallel to each other. The other pyridine group of Hdpyan, being protonated, remains peripheral but involved in a strong [MII-C≡N···Hpy+] hydrogen bond between alternate layers. This provokes a nearly 90° rotation of the plane defined by the [MII(CN)4]2- groups, with respect to the average plane defined by the layers, forcing the observed uncommon bridging mode and the accumulation of negative charge around each FeII, which is compensated by the axial [Hdpyan]+ ligands. According to the magnetic and calorimetric data, both compounds undergo a strong cooperative spin transition featuring a 10-12 K wide hysteresis loop centered at 220 (Pt) and 211 K (Pd) accompanied by large entropy variations, 97.4 (Pt) and 102.9 (Pd) J/K mol. The breaking symmetry involving almost 90° rotation of one of the two coordinated pyridines together with the large unit-cell volume change per FeII (ca. 50 Å3), and subsequent release of significantly short interlayer contacts upon the low-spin → high-spin event, accounts for the strong cooperativity.

Tuning of magnetic properties of Al-doped cobalt ferrite nanofiber prepared by electrospinning technique

The Al-doped cobalt ferrite (CoFe2-xAlxO4) nanofiber has been prepared by employing the electrospinning technique. All the nanofibers are characterized by the XRD technique. The Rietveld refinement of the XRD pattern reveals the spinel cubic structure with the Fd m space group. The TEM micrographs confirm the formation of nanofiber with a nearly uniform diameter of ∼137 ± 10 nm. The magnetic properties of all the nanofibers have been investigated by measuring the M-H hysteresis loops with the help of a Vibrating sample magnetometer (VSM). The M-H loops analysis demonstrates a reduction in the saturation magnetization, and coercivity from 106.88 emu g−1 to 40.01 emu g−1 and 0.897 kOe to 0.324 kOe, respectively, with the increase in Al concentration in the nanofibers. The ‘Law of Approach to Saturation’ technique has been employed to understand the magnetocrystalline anisotropy constant in the samples. The magnetocrystalline anisotropy constant (K 1) decreases with the increase in Al3+ substitution in place of Fe3+ in the spinel cobalt ferrite nanofibers. A squeezing effect on the M-H loop near M = 0 is observed and, it has been analyzed by a hysteresis loop width (∆H) versus magnetization (M) plot. The squeezing effect has been observed due to the exchange interaction phenomenon between the magnetic and non-magnetic atoms in the Al-doped cobalt ferrite nanofiber. The magnetic properties study demonstrates that Al-doped cobalt ferrite nanofiber exhibits soft magnetic nature.

Order-Disorder, Symmetry Breaking, and Crystallographic Phase Transition in a Series of Bis(trans-thiocyanate)iron(II) Spin Crossover Complexes Based on Tetradentate Ligands Containing 1,2,3-Triazoles.

We report herein a series of neutral trans-thiocyanate mononuclear spin crossover (SCO) complexes, [FeIIL(NCS)2] (1-4), based on tetradentate ligands L obtained by reaction of N-substituted 1,2,3-triazolecarbaldehyde with 1,3-propanediamine or 2,2-dimethyl-1,3-diaminopropane [L = N1,N3-bis((1,5-dimethyl-1H-1,2,3-triazol-4-yl)methylene)propane-1,3-diamine/-2,2-dimethylpropane-1,3-diamine, 1/2 and N1,N3-bis((1-ethyl/1-propyl-1H-1,2,3-triazol-4-yl)methylene)-2,2-dimethylpropane-1,3-diamine, 3/4]. The thermal-induced SCO behavior is characterized by abrupt transitions with an average critical temperature (ΔT1/2)/hysteresis loop width (ΔThyst) in the range 190-252/5-14 K, while the photo-generated metastable high-spin (HS) phases are characterized by TLIESST temperatures in the range 44-59 K. Single crystal analysis shows that except 1, all compounds experience reversible symmetry breaking coupled with the thermal SCO. Furthermore, 4 experiences an additional phase transition at ca. 290 K responsible for the coexistence of two HS phases quenched at 10 K through LIESST and TIESST effects. The molecules form hexagonally packed arrays sustained by numerous weak CH···S and C···C/S···C/N···C bonds involving polar coordination cores, while non-polar pendant aliphatic substituents are segregated inside, occupying hexagonal channels. Energy framework analysis of complexes with one step SCO transition (1, 2, and 4) shows a correlation between the cooperativity and the amplitude of changes in the molecule-molecule interactions in the lattice at the SCO transition.

Enhancement of phase transition properties of ultrathin VO2 thin films on microsphere array by vacuum thermal pre-annealing

Vanadium dioxide (VO2) thin films were fabricated on SiO2 microsphere array surface by vacuum thermal pre-annealing and rapid thermal oxidization annealing of magnetron sputtering vanadium films. The effects of vacuum thermal pre-annealing temperature on phase transition properties of VO2 thin films were investigated. The resistance transition ranges of phase transition are improved from 7.58 to 10.23 as the increasing of vacuum thermal pre-annealing temperature. The phase transition temperature decreases and the width of thermal hysteresis loop keeps constant. We analyzed the effects of vacuum thermal pre-annealing temperature on phase transition properties of VO2 thin film in the light of vanadium thin film shrinking effects. The results are important for fabrication of ultrathin VO2 film on microsphere array and application in optical regulation field.

Guest-induced pore breathing controls the spin state in a cyanido-bridged framework.

Iron(ii) spin cross-over (SCO) compounds combine a thermally driven transition from the diamagnetic low-spin (LS) state to the paramagnetic high-spin (HS) state with a distinct change in the crystal lattice volume. Inversely, if the crystal lattice volume was modulated post-synthetically, the spin state of the compound could be tunable, resulting in the inverse effect for SCO. Herein, we demonstrate such a spin-state tuning in a breathing cyanido-bridged porous coordination polymer (PCP), where the volume change resulting from guest-induced gate-opening and -closing directly affects its spin state. We report the synthesis of a three-dimensional coordination framework {[FeII(4-CNpy)4]2[WIV(CN)8]·4H2O}n (1·4H2O; 4-CNpy = 4-cyanopyridine), which demonstrates a SCO phenomenon characterized by strong elastic frustration. This leads to a 48 K wide hysteresis loop above 140 K, but below this temperature results in a very gradual and incomplete SCO transition. 1·4H2O was activated under mild conditions, producing the nonporous {[FeII(4-CNpy)4]2[WIV(CN)8]}n (1) via a single-crystal-to-single-crystal process involving a 7.3% volume decrease, which shows complete and nonhysteretic SCO at T1/2 = 93 K. The low-temperature photoswitching behavior in 1 and 1·4H2O manifested the characteristic elasticity of the frameworks; 1 can be quantitatively converted into a metastable HS state after 638 nm light irradiation, while the photoactivation of 1·4H2O is only partial. Furthermore, nonporous 1 adsorbed CO2 molecules in a gated process, leading to {[FeII(4-CNpy)4]2[WIV(CN)8]·4CO2}n (1·4CO2), which resulted in a 15% volume increase and stabilization of the HS state in the whole temperature range down to 2 K. The demonstrated post-synthetic guest-exchange employing common gases is an efficient approach for tuning the spin state in breathing SCO-PCPs.

Innovative connections for steel-concrete-trussed beams: a patented solution

The most recent design strategies welcome the adoption of innovative techniques for seismic energy input mitigation, aiming to achieve high dissipation capacity, prevent the structure from collapse and ensure the serviceability of the construction. Friction damper devices have been widely adopted in framed steel structures for decades, while their introduction in different structural types is still under investigation. This paper presents the outcomes of innovative research supported by the industry and conducted on beam-to-column connections of RC structures in which the beams are Hybrid Steel-Trussed Concrete Beams (HSTCBs) and the columns are classical RC pillars. An innovative solution, recently patented, has been found for the mitigation of the effects of seismic cyclic actions on small-sized beam-column joints, typically characterised by a large amount of longitudinal reinforcement due to the small effective depth of the beam. This paper collects the main featuring steps of the innovative research, which has led to the patented solution. The calculation procedure for designing the proposed connection is shown, and the validation through 3D finite element modelling is described. For the structural analysis of the joint, several monotonic and cyclic simulations have been carried out with the scope of investigating different design moment values. The finite element results proved that the patented solution is effective in preventing beam, column and joint from damage and it is suitable for exhibiting adequate dissipative capacity ensured by a flexural behaviour dominated by wide and stable hysteresis loops.

Experimental and numerical assessment of a steel frame equipped with Dissipative Replaceable Bracing Connections

In the last decades, high priority has been given by the research community to the development of low-damage structures, and reparability has become fundamental for minimizing the environmental and economic impact of reconstruction. In this context, the European Research Fund for Coal and Steel (RFCS) project DISSIPABLE was carried out, with the aim to test large-scale structures where the dissipation is concentrated on replaceable components introduced in the structure. In this paper, the performance of a six-storey braced steel frame with dissipative systems is analysed. The capacity of withstanding seismic actions relies on Dissipative Replaceable Bracing Connections (DRBrC), used for the brace-column joints. The energy dissipation is ensured by wide hysteresis loops experienced by DRBrC, whose configuration enables an easy replacement after a medium-high intensity earthquake. Results of a wide experimental test campaign on full-scale structures and numerical analyses on refined models are presented and compared. In particular, experimental data were used to validate and to calibrate the simplified numerical laws used to represent the cyclic performance of the dissipative components and it was proved the effectiveness of using a simplified formulation from both a theoretical and a practical point of view.

Two-Dimensional Coordination Polymer Showing Spin-Crossover Behavior with a 64 K Wide Hysteresis Loop.

A two-dimensional grid-like coordination polymer, [Fe(NCBH3)2(Py2ttz)2]·4CHCl3 (1·4CHCl3, Py2ttz = 2,5-di(pyridin-4-yl)thiazolo[5,4-d]thiazole), showed one-step complete spin crossover with unexpectedly large hysteresis loop of 64 K wide and temperature-induced excited spin-state trapping effect below 91 K.

Scalable room-temperature dielectric switchable composites with giant contrast ratio and great cycle stability

Room-temperature dielectric switching materials are highly desirable for many potential industrial applications in smart electronic/electrical engineering fields, but they suffer from key limitation of poor integration of remarkable dielectric switching properties, promising scalability, and low cost. Here, a general solution to solve this problem is demonstrated to attain an excellent cost/performance balance. By mixing ionic liquids (ILs) with polyethylene glycol (PEG), an all-organic composite enables an ultrahigh dielectric switching ratio above 320.6 at 34.2 Hz, almost 100% dielectric constant retention after 500 cycles, the highest attainable to a ∼35 °C wide thermal hysteresis loop, and tunable dielectric transition temperature. Also, the PEG/ILs can defeat the conflict of dielectric switching properties versus cost, namely impressive dielectric switching properties are achieved through simple mixing of commercialized components without solvent. The findings offer promise for highly efficient, scalable, low-cost, and environmentally friendly preparation of high-performance room-temperature dielectric switching materials.

Ultra‐Tough Room‐Temperature Dielectric Switching Ionic Gels with Long‐Cycle Stability

AbstractAs a favorable candidate for the next‐generation smart electronic devices, thermo‐responsive dielectric materials are faced with two crucial challenges: insufficient mechanical toughness and lack of the combination of promising dielectric switching properties, desired mechanical properties, and long‐cycle stability. Herein, a new scalable strategy is proposed for designing thermo‐responsive dielectric switching materials that simultaneously integrate the individual features, such as promising dielectric switching properties, outstanding mechanical properties, and great cycle stability, into one gel, based on a new dual dielectric switching mechanism induced by interfacial structure evolution. The ionic gel can readily achieve a superb combination of distinct reversible dielectric bistability, a high dielectric switching ratio above 150, a ≈15 °C wide thermal hysteresis loop, and tunable room‐temperature dielectric transition behavior, impressive high ductility, desirable high mechanical strength, record‐high stability of at least 1000 cycles. Such an all‐in‐one design enhances the adaptability to multiple application scenarios, durability, and a lifetime of the dielectric switching gels. Together with the facile fabrication process and recyclable thermoplastic system, thereby contributing to cost and energy saving, this research provides a feasible and sustainable strategy for constructing highly desirable thermo‐responsive dielectric switching materials.

Critical and hysteresis phenomena in the mixed spin-[formula omitted] anisotropic two-dimensional Heisenberg model: A Monte Carlo study

The critical and hysteresis behaviors of the ferromagnetic mixed-spin system consisting of two sublattices A and B with two types of spins SA=32 and SB=12 described by anisotropic Classical-Heisenberg Model on a square lattice are examined by using Monte Carlo simulations based on metropolis algorithm. By exploiting the thermal variations of the order-parameters and the magnetic susceptibility, the phase diagrams are calculated on the (Dz/J,kBT/J), (Dx/J,kBT/J) and (Δ,kBT/J) planes and the effects of various interaction parameters in the Hamiltonian are explored. It is found that the model yields only second-order phase transitions. We have also estimated the critical exponents ν, β and γ of the model as functions of Dz and Dx by using the finite-size scaling arguments and found that they depend on the details of the model. Finally, the hysteresis behavior of the model is also investigated and it is revealed that the width of hysteresis loop decreases with temperature while it increases for positive Dz values.

Slow Phase Transition-Induced Scan Rate Dependence of Spin Crossover in a Two-Dimensional Supramolecular Fe(III) Complex

Slow Phase Transition-Induced Scan Rate Dependence of Spin Crossover in a Two-Dimensional Supramolecular Fe(III) Complex

Explosive synchronization of weighted mobile oscillators

In recent years, explosive synchronization (ES) has attracted extensive interest due to its great significance in the study of epileptic seizures and cascading failures in the real world. In this paper, a weighting method based on the frequency mismatches and distances between linked oscillators is proposed to construct a Kuramoto-like model to study ES of mobile oscillators. An interesting phenomenon that the weighting of oscillators can induce a sudden and irreversible synchronization transition with hysteresis loop is revealed. The transition between continuous synchronization and ES can be tuned by the weighting factors. Moreover, it is found that the critical coupling strength and hysteresis loop width are affected by the initial frequency distribution, the number of oscillators, the communication radius, the setting of boundary conditions and the constant absolute velocity of oscillators.