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An induction hysteresigraph using 50 Hz sine wave fields of 7 kOe maximum amplitude, generated by a solenoid-type multilayer coil, suitable for small amounts (down to tens of milligram) of magnetic materials is proposed. The changes in field and magnetization are detected by a field sensing coil and a compensated pick-up coil system, respectively, the as-induced signals being processed by two analog measuring channels (channel H and channel M), whose output signals reproduce the time evolution H(t) and M(t) of the two quantities. These signals are recorded via PC-assisted analog-to-digital conversion and then subjected to final numerical correction and calibration; apart from the demagnetizing field correction, the possible errors caused by the stray flux generated by the magnetized sample itself are also taken into account. In addition, instead of weak signals denoising via standard filtering or smoothing algorithms, reconstruction based on flexible combinations of transition-type fitting functions of time periodic argument is proposed. To prevent signal waveform distortions that can be caused by the frequency-dependent response of channel M, a thorough analysis is carried out in the time domain, by simulating the run of a 100 kHz bandwidth severe test signal, across the stages of this channel. This signal consists of sharp ac pulses, built as a digital replica of the electromotive force induced in a pick-up coil containing the sample, during its evolution along a steep-sided hysteresis loop; an original method, using a small number of parameters, is proposed to build the spectral expansion of the test signal. [ABSTRACT FROM AUTHOR]

Two effects must be considered for the purpose of comparing hysteresis loops of hard magnetic materials (e.g., Nd–Fe–B magnets), measured in open circuit (e.g., vibration sample magnetometer or extraction magnetometer) to those measured in closed circuit (i.e., in a hysteresigraph). The first of these is related to the influence of magnetic viscosity during magnetization reversal, which reduces coercivity. Due to longer measurement times with magnetometers compared to hysteresigraphs (typically 100 s versus 1 s), the coercive field is reduced more in open-circuit measurements than in closed-circuit ones, by typically 20 kA/m. The second effect to be considered is due to differences in various contributions to the demagnetizing field. The slope of the magnetization variation in open-circuit loops is different to that due to the usually considered demagnetizing effects (applicable to soft materials). A reduction in the open-circuit coercive field value compared to the closed-circuit one is found, which is of the order of 25 kA/m for the systems discussed here. This is attributed to the fact that the reversal process itself is affected by how the measurement is made. Reversal has less collective character during open-circuit than during closed-circuit measurements. [ABSTRACT FROM AUTHOR]

The standard method for measuring magnetic properties of permanent magnets is the closed circuit method using an iron-cored electromagnet. With the advances of modern high quality permanent magnetic materials, it has become more and more important to measure their magnetic properties accurately both at room and elevated temperatures. Many problems have arisen when using this traditional DC hysteresigraph to test these new materials, such as those based on rare earth intermetallic compounds, bonded magnetic materials and nanocrystalline exchange-coupled magnets. The physical knowledge on these principal problems including magnetic properties of material, magnetic properties of product, specimen, uniform magnetization, saturation magnetization, the influence of the saturation of the poles, and the influence of Hall probe, etc., is important in the research and development of new materials and also nondestructive evaluation (NDE). These problems are discussed in this paper qualitatively and the current statuses to solve these problems are also presented. [ABSTRACT FROM AUTHOR]

Presents a study on vector generalization of the critical model for superconducting hysteresis. Factors considered in the study; Boundary value problem presented; Conclusion.

Quality of a scanning electron microscopy (SEM) image is strongly influenced by noise. This is a fundamental drawback of the SEM instrument. Complex hysteresis smoothing (CHS) has been previously developed for noise removal of SEM images. This noise removal is performed by monitoring and processing properly the amplitude of the SEM signal. As it stands now, CHS may not be so utilized, though it has several advantages for SEM. For example, the resolution of image processed by CHS is basically equal to that of the original image. In order to find wide application of the CHS method in microscopy, the feature of CHS, which has not been so clarified until now is evaluated correctly. As the application of the result obtained by the feature evaluation, cursor width (CW), which is the sole processing parameter of CHS, is determined more properly using standard deviation of noise Nσ. In addition, disadvantage that CHS cannot remove the noise with excessively large amplitude is improved by a certain postprocessing. CHS is successfully applicable to SEM images with various noise amplitudes. SCANNING 35:292-301, 2013. © 2012 Wiley Periodicals, Inc [ABSTRACT FROM AUTHOR]

In this paper a modified Direct Torque Control (DTC) scheme for Brushless DC Motors is presented. The aim of this modification is to overcome the problem of variable switching frequency and high torque ripple in conventional hysteresis based controllers of DTC drives. Also with a new modified switching table and a new torque controller, the power recovery and electrical braking performance of BLDC motors are improved. As it is known, in DTC drives for BLDC motors there is a commutation torque ripple, which occurs every 60 electrical degrees. In this novel method, these commutation ripples are completely eliminated by employing the threephase switching table in the preceding time of the commutation periods. This novel method has a simple control structure which is compatible with principle of conventional DTC scheme. In classic DTC drives, the switching frequency is variable. In this paper, in order to obtain a fix switching frequency, a new and simple torque controller is introduced, to replace the conventional hysteresis comparator. These simple modifications have significantly improved the performance of the DTC drive system, while at the same time all the advantages of the basic DTC are still retained. Simulation results have shown the proposed modified DTC scheme causes apparent reduction of the torque ripple and maintaining a constant switching frequency, compared with conventional DTC drives for BLDC motors. [ABSTRACT FROM AUTHOR]

The electrical hysteresis of polysilicon thin-film transistors (poly-Si TFTs) employing a negative data insertion (NDI) has been investigated. It is known that the image sticking in active-matrix organic light emitting diode displays using the poly-Si TFT back plane was mainly caused by the hysteresis of driving TFT in a pixel. In this paper, we propose a type of NDI method using inverse data signals in order to suppress the hysteresis of poly-Si TFTs. Experimental results show that the NDI was very effective to reduce the hysteresis level of poly-Si TFTs induced by carrier trapping and detrapping. [ABSTRACT FROM AUTHOR]

The role of magnetic domains (and the walls between domains) in determining the electrical properties of ferromagnetic materials has been investigated in great detail for many years, not least because control over domains offers a means of manipulating electron spin to control charge transport in ‘spintronic’ devices. In contrast, much less attention has been paid to the effects of domains and domain walls on the electrical properties of antiferromagnets: antiferromagnetic domains show no net external magnetic moment, and so are difficult to manipulate or probe. Here we describe electrical measurements on chromium—a simple metal and quintessential spin density wave antiferromagnet—that show behaviour directly related to spin density wave formation and the presence of antiferromagnetic domains. Two types of thermal hysteresis are seen in both longitudinal and Hall resistivity: the first can be explained by the quantization of spin density waves due to the finite film thickness (confirmed by X-ray diffraction measurements) and the second by domain-wall scattering of electrons. We also observe the striking influence of the electrical lead configuration (a mesoscopic effect) on the resistivity of macroscopic samples in the spin density wave state. Our results are potentially of practical importance, in that they reveal tunable electrical effects of film thickness and domain walls that are as large as the highest seen for ferromagnets. [ABSTRACT FROM AUTHOR]

The authors study evolution hemivariational inequalities of semilinear type containing a hysteresis operator. For such problems we establish an existence result by reducing the order of the equation and then by the use of the time-discretization procedure. [ABSTRACT FROM AUTHOR]

This research work concerns the hydriding reaction of LaNi5 during the first hydriding cycles (activation process). Step-by-step sorption isotherms (Δ[H/M] ≈ 0.03) were measured at 298 K, in the composition range 0 < H/M < 2.0, at the beginning (first hydriding cycle, where hysteresis is maximum) and at the end (tenth hydriding cycle, where hysteresis is minimum) of the activation process, offering the possibility to correlate thermodynamic states (pressure-composition data points) to sorption kinetics. Using pneumatochemical impedance spectroscopy (PIS), experimental impedance diagrams were obtained for each data point of the isotherms. Microscopic rate parameters such as surface resistance and hydrogen diffusion coefficient were obtained as a function of composition, by fitting appropriatemodel equations to experimental impedances. It is found that the high-frequency pneumatochemical resistance significantly decreases during activation. This is correlated with the surface increase of the solid-gas interface area. The hydrogen diffusion coefficient is found to be larger at the beginning of the activation process and lower on a fully activated sample. [ABSTRACT FROM AUTHOR]

We report on an interlaboratory study on the precision and accuracy of determining dc soft magnetic properties, under the auspices of ASTM Committee A06 on Magnetic Properties. For certain quantities, the significant differences in the between-laboratory reproducibility results for high-permeability materials indicate that there is a need for improvement in the equipment and software procedures of measurement systems. [ABSTRACT FROM AUTHOR]

This paper deals with the diffusion of rotating electromagnetic fields into hysteretic materials. A simplified vector formulation based on a parallelogram hysteresis model has been investigated, in order to significantly reduce the computational effort. Vector saturation and loss properties are discussed. The whole simulation has been done by the use of a finite-element time-domain algorithm. [ABSTRACT FROM AUTHOR]

Abstract: Hysteresis typically refers to subcritical transitions between two stable attractors at two different values of a control parameter. We address here a different form of hysteresis, referred to as complex hysteresis, where a stable attractor and a chaotic attractor coexist. However, depending on the direction of variation of the control parameter, the chaotic state can be observed or cannot be observed. We address the phenomenon of complex hysteresis in one-dimensional maps as well as in a real flow. [Copyright &y& Elsevier]

For type I superconductors with penetration parameter λ below a certain critical value, the existence of multiple local minimizers of the energy functional is shown. The behavior of these minimizers is examined when the Ginzburg–Landau parameter is small, and a hysteresis phenomenon is demonstrated. In contrast to the case investigated by X. B. Pan [J. Math. Phys. 44, 2639 (2003)] where λ is above the critical value, the results presented in this paper show that type I superconductors with λ below the critical value have higher critical magnetic field Hc, and exhibit more complicated superconducting behavior. [ABSTRACT FROM AUTHOR]

This work proposes a methodology to estimate core losses under pulsewidth modulation (PWM) or de bias ripple voltage excitations. A special hysteresisgraph was built to measure toroidal samples under pulsed voltages. An experimental methodology, based on the principles of ferromagnetism, was implemented to investigate minor loop losses in toroidal samples of oriented and nonoriented FeSi. Triangular induction waveforms with constant dB/dt were generated. The results demonstrated that minor loops produced by PWM voltage, do not affect the major hysteresis loop losses nor the losses of other minor loops measured at different points of the major loop. In these experiments, minor loop losses under PWM voltage were very similar to minor loop losses under dc bias ripple voltage. Aspects of the behavior of minor loop losses as a function of amplitude and magnetic flux density are reported in this work. [ABSTRACT FROM AUTHOR]

It is well known that hysteresis is a principal source of internal energy dissipation in structural systems. One of the widely accepted hysteretic models for structures is a differential model, called the modified Bouc-Wen model. In this paper, a constrained Kalman filter with a global weighted iteration strategy has been used to estimate the parameters in the modified Bouc-Wen model. An actual seismic signal was used to excite a nonlinear structural system described by the modified Bouc-Wen model that has both degradation and pinching characteristics. The convergence results show that, for both clean and noise-corrupted data, this algorithm is effective in estimating all the 11 parameters with satisfactory precision and fast convergence. As this algorithm has modest computing requirements, it should be acceptable as a basic tool for estimating hysteretic parameters in engineering design. [ABSTRACT FROM AUTHOR]

Digital hysteresisgraph can be used for the measurement of dynamic hysteresis loops up to 100 kHz. Digital feedback allows achievement of sinusoidal flux density by iterative modification of the excitation voltage waveform. This approach is used for the measurement of closed (toroidal) samples at higher frequencies. [Copyright &y& Elsevier]

Presents information on a study which characterized the statistical properties of Barkhausen noise in a epitaxial iron film grown on magnesium oxide. Use of a focused magnetooptical hysteresigraph; Methodology; Results and discussion.

The properties of the Barkhausen noise in a series of permalloy squares have been measured with a magneto-optical hysteresigraph. The magnetic structures have been litographically defined in a permalloy film (thickness 160 nm) as squares having a size from 20 to 320 μm. The statistical distributions of the most significant parameters of the Barkhausen jumps have been extracted from the original data. At variance with respect to bulk and thin films, the jump amplitude distribution does not follow a well-defined power-law behavior. This observation is explained in terms of a transition between a discrete magnetization regime typical of small magnetic structures and the more usual regime observed in extended samples. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents information on a study which developed a large bore pulsed field hysteresigraph system used for characterizing permanent magnets. Significance of pulse field magnetometer; Description of the system; Procedure of calibration; Tests conducted on the system; Conclusion.

Abstract: Hysteresis may be defined as ‘the retardation or lagging of an effect behind the cause of the effect’. The two main reasons for the lag phase are limited access to the site of drug action or slow receptor kinetics. Both of these characteristics would produce an anticlockwise hysteresis, in which time moves anticlockwise in the change in the relationship between plasma concentration and observed effect with time. An alternative definition would be ‘failure of one of two related phenomena to keep pace with the other’, and would include any situation in which the value of one variable depends on whether the other variable is increasing or decreasing. This definition would take in clockwise hysteresis, which is seen in drug tolerance. [Copyright &y& Elsevier]

This paper investigates the design of an iteration-based controller combined with feedback control to address the positioning error caused by hysteresis in a shape memory alloy (SMA) actuator. Without compensation, the positioning error due to hysteresis can be excessively large (greater than 20%), therefore limiting the performance of SMAs in positioning applications. An iterative controller based on the Preisach hysteresis model is used to compensate for the hysteresis. However, one of the major challenges with SMA at or near the phase-transition zones, from martensite to austenite and vice versa, is the output response is shown to be sensitive to small changes in the input. In practice, an iterative controller provides limited performance due to lack of robustness. It is demonstrated that combining a simple feedback controller with an iterative controller provides the needed robustness to enable high-precision tracking. Experimental results are presented that show maximum tracking error of 0.15% of the total displacement range—this value is approximately the noise level of the sensor measurement. [ABSTRACT FROM AUTHOR]

The magnetization process in a square dot of permalloy having a size of 20 μm and 80 nm thickness has been investigated with a focused magneto-optical hysteresigraph. With this apparatus, it is possible to measure in a few seconds the hysteresis loop with a signal-to-noise ratio adequate for the observation of Barkhausen jumps also in such a small magnetic sample. From a sequence of 6000 loops, systematic data on the statistical properties of these jumps have been extracted. The observed behavior shows strong deviations with respect to the available data on bulk samples and thin films. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]