Search results for "Hysteresi"

Nucleation and Collapse of the Superconducting Phase in Type-I Superconducting Films

2005

The phase transition between the intermediate and normal states in type-I superconducting films is investigated using magneto-optical imaging. Magnetic hysteresis with different transition fields for collapse and nucleation of superconducting domains is found. This is accompanied by topological hysteresis characterized by the collapse of circular domains and the appearance of lamellar domains. Magnetic hysteresis is shown to arise from supercooled and superheated states. Domain-shape instability resulting from long-range magnetic interaction accounts well for topological hysteresis. Connection with similar effects in systems with long-range magnetic interactions is emphasized.

Dynamic Preisach Hysteresis Model for Magnetostrictive Materials for Energy Application

2013

In this paper the magnetostrictive material considered is Terfenol-D. Its hysteresis is modeled by applying the DPM whose identification procedure is performed by using a neural network procedure previously publised [. The neural network used is a multiplayer perceptron trained with the Levenberg-Marquadt training algorithm. This allows to obtain the Preisach distribution function, without any special conditioning of the measured data, owing to the filtering capabilities of the neural network interpolators. The model is able to reconstruct both the magnetization relation and the Field-strain relation. The model is validated through comparison and prediction of data collected from a typical …

Spin-crossover nanocrystals with magnetic, optical, and structural bistability near room temperature.

2008

Spin crossover behavior under pressure of Fe(PM-L)2(NCS)2 compounds with substituted 2′-pyridylmethylene 4-anilino ligands

1998

Abstract New iron(II) spin crossover systems with large aromatic ligands, based on 2′-pyridylmethylene 4-anilino units, have been synthesized and studied. The whole range of spin crossover behavior has been observed, starting from pure high-spin to more or less complete gradual transitions and finally to discontinuous type transitions with both small and large hysteresis. Magnetic measurements under pressure have revealed that two of the compounds exhibit pressure-induced new phases with larger hysteresis than at atmospheric pressure. For one of the compounds the formation of this new phase is irreversible and the hysteresis width is ∼100 K, as compared to 37 K before applying pressure.

Vacuum deposited perovskite solar cells employing dopant-free triazatruxene as the hole transport material

2017

Abstract Planar perovskite solar cells using organic charge selective contacts were fabricated. In a vacuum deposited perovskite-based solar cell, dopant and additive free triazatruxene as the hole transport layer was introduced for device fabrication. High open-circuit voltage of 1090 mV was obtained using methylammonium lead iodide (Eg=1.55 eV) as light harvesting material, thus representing a loss of only 460 mV which is in close vicinity of mature silicon technology (400 mV). The devices showed a very competitive photovoltaic performance, monochromatic incident photon-to-electron conversion efficiency of 80% and the power conversion efficiencies in excess of 15% were measured with a neg…

Study of charge density waves in suspended 2H-TaS 2 and 2H-TaSe 2 by nanomechanical resonance

2021

The charge density wave (CDW) state in van der Waals systems shows interesting scaling phenomena as the number of layers can significantly affect the CDW transition temperature, $T_{CDW}$. However, it is often difficult to use conventional methods to study the phase transition in these systems due to their small size and sensitivity to degradation. Degradation is an important parameter which has been shown to greatly influence the superconductivity in layered systems. Since the CDW state competes with the onset of superconductivity, it is expected that $T_{CDW}$ will also be affected by the degradation. Here, we probe the CDW phase transition by the mechanical resonances of suspended 2H-TaS…

Pressure-induced hysteresis in the high spin \leftrightarrow low spin transition in bis(2,4-bis(pyridin-2-yl)thiazole) iron(II) tetrafluoroborate

2008

Studies of the spin transition behavior of the mononuclear compound [Fe(pythiaz)2](BF4)2 have been carried out under hydrostatic pressures up to 9.13 kbar in the 5–300 K temperature range. Under ambient pressure this compound exhibits an approximately half-step (incomplete) HS ↔ LS transition with T1/2 = 146 K without any thermal hysteresis. At pressures up to 4.5 kbar the behavior remains similar but with an upward displacement of T1/2 and a slight decrease in the residual high spin fraction at low T . Application of higher pressures resulted in an almost complete two-step spin transition with several unusual pressure effects. Along with the expected pressure dependence of T1/2 the surpris…

Magnetic Stochastic Resonance in systems described by Dynamic Preisach Model

2008

Stochastic resonance (SR) is generally considered as an enhancement of the system response for certain finite values of the noise strength. In particular the signal to noise ratio (SNR) and the signal amplification show a maximum as a function of the noise intensity. This effect has been experimentally observed in many physical systems and also in magnetic systems. However, as far as magnetic systems are concerned, the dynamic features of the systems have been neglected and it has been assumed that the typical relaxation time is negligible. However this is clearly a rough approximation. In order to clarify this relation, in this paper we numerically study magnetic stochastic resonance in se…

Eddy covariance and sap flow measurement of energy and mass exchange of woody crops in a Mediterranean environment

2012

Evapotranspiration estimation by micrometeorological techniques through the assessment of mass and energy exchanges in the soil-plant-atmosphere continuum (SPAC) is a very active research area, involving both well-known and novel measurement techniques. A crucial aspect in validating experimental results is the integration of independent measurements of mass and energy exchanges in the SPAC. To this aim, the development and validation of an integrated approach in major tree crop species, involving different independent techniques, are presented. Eddy covariance estimates of ET fluxes were compared to up-scaled sap flow measurements in olive, orange and grapevine, three important Mediterrane…

Forming pressure dependence of the ferroelectric domain structure in green barium titanate pellets

1995

Abstract Modifications of the X-ray diffraction line profiles by die pressing of fine grained powders of barium titanate have been studied. Two main parameters have been considered: the forming pressure and the mechanical characteristics of the binder. The higher the forming pressure, the greater the modifications of the line profiles. Furthermore, the phenomena seems to be related to pressing only; no significant effect related to the nature of the binder has been shown. The modifications of the diffraction line profiles are interpreted by considering a reduction of the size of the ferroelectric domains during pressing. In order to confirm this interpretation, the behaviour of the domain s…