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Among non-destructive testing methods, a group dedicated to the assessment of the state of residual stresses can be distinguished. The method of measuring residual stresses using the Barkhausen noise method has many advantages, as evidenced by the number of publications. The residual stresses in metal products are important for the further processing of such metal, such as laser cutting or bending. The results presented in this work are of an experimental nature, and the presented method of calibration of measuring heads shows how various research techniques can be used to correlate results. The research was carried out for structural steel due to the market share of this type of steel. The method can be used to measure the residual stresses in ferromagnetic metal products in order to assess their directions and quantify them. A prerequisite for the use of this measurement method is that the amplitude and geometry of the Barkhausen noise are adequately correlated to the specific values of the state of stress depending on the tested steel grade or other metals. In this study, a method for calibrating measuring sensors for the residual stress measurements is presented, as developed by the authors. The method involved conducting bending tests in both numerical modeling and experimental tests. During the bending tests, changes in the magnetic field (Barkhausen noise waveform) were recorded, taking into account the state of elastic stresses. Correlating the results of the numerical calculations and Barkhausen noise measurements made it possible to determine the quantitative values of the residual stresses in the steel sheets. Thanks to the method used, very accurate measurement is possible, and the obtained results are repeatable. [ABSTRACT FROM AUTHOR]

The relationship between the change in the structural and mechanical properties of metal materials and structural elements and the modification of their magnetic behaviour under the influence of mechanical stresses, temperature and aggressive environments is established in order to create a methodology for both determining the residual resource and increasing the operational reliability of materials and systems. An express method of microstructure assessment by means of determining the change in the magnetoacoustic response of the material is proposed. [ABSTRACT FROM AUTHOR]

Among non-destructive testing methods, a group dedicated to the assessment of the state of residual stresses can be distinguished. The method of measuring residual stresses using the Barkhausen noise method has many advantages, as evidenced by the number of publications. The residual stresses in metal products are important for the further processing of such metal, such as laser cutting or bending. The results presented in this work are of an experimental nature, and the presented method of calibration of measuring heads shows how various research techniques can be used to correlate results. The research was carried out for structural steel due to the market share of this type of steel. The method can be used to measure the residual stresses in ferromagnetic metal products in order to assess their directions and quantify them. A prerequisite for the use of this measurement method is that the amplitude and geometry of the Barkhausen noise are adequately correlated to the specific values of the state of stress depending on the tested steel grade or other metals. In this study, a method for calibrating measuring sensors for the residual stress measurements is presented, as developed by the authors. The method involved conducting bending tests in both numerical modeling and experimental tests. During the bending tests, changes in the magnetic field (Barkhausen noise waveform) were recorded, taking into account the state of elastic stresses. Correlating the results of the numerical calculations and Barkhausen noise measurements made it possible to determine the quantitative values of the residual stresses in the steel sheets. Thanks to the method used, very accurate measurement is possible, and the obtained results are repeatable.

Cylindrical ferromagnetic nanowires are of particular interest in nanomaterials science due to various manufacturing methods and a wide range of applications in nanotechnology, with special attention given to those with diameters less than the single domain limit. In the current study, the simulations of magnetic properties of isolated iron nanowires with a diameter of 5 nm and various aspect ratios, as well as two types of arrays of such nanowires (with hexagonal and square arrangement), were performed using atomistic spin model. In the case of a single nanowire, change of coercive field for different applied field directions with aspect ratio was discussed. It was shown that the evolution of the magnetization reversal mechanism from coherent rotation to domain wall propagation appears with increasing length of single nanowire. For the arrays of cylindrical nanostructures, it was revealed that different number of nearest neighbors for each nanostructure in square and hexagonal arrays have an influence on their magnetostatic interactions, which are the most significant for shortest interwire distances. The corresponding spin configurations during the remagnetization process showed the appearance of intermediate magnetization states (when a part of wires is magnetized parallel and part antiparallel to the field direction), connected with Barkhausen effect, which influence the observed hysteresis curves. [ABSTRACT FROM AUTHOR]

We present the study of domain structure evolution during polarization reversal in lithium niobate crystal with an initial tailored polydomain state representing a matrix of isolated domains arranged in a square lattice. Domain kinetics during switching differs significantly from the initial single domain state. Growing domains elongate in Y crystallographic direction coinciding with the 2D lattice direction. The field dependence of main domain walls follows the activation law. Typical switching current consists of many Barkhausen pulses separated by low current regions. Korcak's analysis of switching current has demonstrated the Hurst exponent below 0.5, which indicates an anti-persistent character of the process. [ABSTRACT FROM AUTHOR]

The continuous and jumpwise components of the magnetic relaxation were analyzed in the (NdDy)(FeCo)B sintered magnets in the stationary magnetic field close to the coercive field. The jumpwise magnetic relaxation of the extremely low frequency (∼0.01–0.1 Hz) and a large average amplitude (∼0.2%) of the saturation magnetization were revealed. The 2%–3% Sm doping ions increase the continuous relaxation up to 2 times and decrease the magnetization probability and average jump size down to 1.5 times. The spectral power of the magnetization jumps corresponds to the white noise appearing due to the uncorrelated individual magnetization reversal of the ∼103 independent grains. The continuous relaxation is due to the domain wall motion. Magnetic force microscopy allows us to distinguish the domain walls shift and the reversal of the grains to estimate the energy and width of the domain walls. First order reversal curve analysis revealed the contribution of the 2-14-1 phase and isolated 1-4-1 phase inclusions and the effect of Sm doping on the distribution of the switching and interaction fields of these phases. [ABSTRACT FROM AUTHOR]

Using nondestructive techniques to quantitatively estimate residual stresses along the depth is necessary to improve the ability to predict the real fatigue life of pieces for many applications. Magnetic Barkhausen noise has been proven to successfully estimate the residual stress at the surface produced by machining, plastic deformation, phase transformation or surface treatments such as shot peening, also allowing one to obtain information of the residual stress depth-profile in shot peened pieces which presented similar depth-profile shapes. However, residual stress depth-profiles with nonmonotonic or different shapes have not been successfully estimated. In the present study, an extended approach is developed in order to estimate these stresses independent of the shape of the residual stress depth-profile. The approach proposed here improves an existing model of the Barkhausen noise spectrum (Kypris-Jiles model) by adding the effect of the attenuation of the applied magnetic field on the Barkhausen noise. This extended approach is used to estimate the residual stress depth-profiles of samples with different depth-profiles using a calibration process. The approach is validated by estimating the residual stress depth-profiles, with errors smaller than 70 MPa in a depth of 130 μm, in all the samples studied. [ABSTRACT FROM AUTHOR]

Self-powered magnetic sensors are fundamental for the development of Industry 4.0, the Internet of things (IoT), wireless sensor networks, unmanned vehicles, smart cities, and sustainability. This review aimed to elucidate the working principles, materials, manufacture, output properties, and perspectives of Wiegand sensors. A Wiegand sensor is composed of a magnetic sensing wire, which is called a Wiegand wire, and a pick-up coil for the output of an electrical signal and energy. The Wiegand sensor requires an external magnetic field of about 70 Gauss to induce Wiegand wire flux changes, which, in turn, generate an output pulse in the pick-up coil. Output energy of more than 3000 nJ per single pulse (open circuit) can be harvested. The output pulse is derived from the large Barkhausen effect. Therefore, the behavior of the sensor output is independent of the triggering and sensing frequencies. The objective of this review article was to comprehensively highlight research endeavors devoted to Wiegand sensors. Furthermore, application scenarios of current research results are highlighted to find potential gaps in the literature and future contributions. Perspectives and research opportunities of Wiegand sensors are proposed. [ABSTRACT FROM AUTHOR]

The single crystal of a chiral magnet Cr1/3NbS2 exhibits discrete changes in magnetization (M) in response to changes in magnetic field (H) triggered by the formation of a chiral soliton lattice (CSL). In order to provide evidence of this phenomenon, the study of the size effect is indispensable. We investigated the effects of size on this phenomenon by the use of two single crystals, (A) and (B), whose crystal sizes along the c-axis were 110 µm and 60 µm, respectively. First, in (A), the large jumps of M observed in the process of decreasing H exhibited inconsistent features, whereas the largest and second-largest jumps in (B) exhibited reproducibility for both the value of H and the magnitude of the M jumps. This confirms that these large jumps do not originate from the Barkhausen effect, as this effect would result in M jumps appearing at random values of H. When the system size of a sample becomes smaller, the features of the Barkhausen effect are suppressed. Second, as for the successive jumps observed in the H region where the rapid change in M is entirely seen for both the samples, the number of observed M jumps for (B) is more than that for (A). Indeed, the number of the domain wall due to the 2π-soliton in the CSL increases, as the c-axis length of the single crystal increases. However, a series of M jumps must appear in a limited H region below the critical field of the order of 2 kOe. The greater the number of M jumps, the more difficult the detection of the M jump will be in the H resolution of the present setup. Thus, the effects of size on the M jumps observed in the present setup can be understood within the framework of the CSL formation. [ABSTRACT FROM AUTHOR]

The single crystal of a chiral magnet Cr1/3NbS2 exhibits discrete changes in magnetization (M) in response to changes in magnetic field (H) triggered by the formation of a chiral soliton lattice (CSL). In order to provide evidence of this phenomenon, the study of the size effect is indispensable. We investigated the effects of size on this phenomenon by the use of two single crystals, (A) and (B), whose crystal sizes along the c-axis were 110 µm and 60 µm, respectively. First, in (A), the large jumps of M observed in the process of decreasing H exhibited inconsistent features, whereas the largest and second-largest jumps in (B) exhibited reproducibility for both the value of H and the magnitude of the M jumps. This confirms that these large jumps do not originate from the Barkhausen effect, as this effect would result in M jumps appearing at random values of H. When the system size of a sample becomes smaller, the features of the Barkhausen effect are suppressed. Second, as for the successive jumps observed in the H region where the rapid change in M is entirely seen for both the samples, the number of observed M jumps for (B) is more than that for (A). Indeed, the number of the domain wall due to the 2π-soliton in the CSL increases, as the c-axis length of the single crystal increases. However, a series of M jumps must appear in a limited H region below the critical field of the order of 2 kOe. The greater the number of M jumps, the more difficult the detection of the M jump will be in the H resolution of the present setup. Thus, the effects of size on the M jumps observed in the present setup can be understood within the framework of the CSL formation. [ABSTRACT FROM AUTHOR]

Self-powered magnetic sensors are fundamental for the development of Industry 4.0, the Internet of things (IoT), wireless sensor networks, unmanned vehicles, smart cities, and sustainability. This review aimed to elucidate the working principles, materials, manufacture, output properties, and perspectives of Wiegand sensors. A Wiegand sensor is composed of a magnetic sensing wire, which is called a Wiegand wire, and a pick-up coil for the output of an electrical signal and energy. The Wiegand sensor requires an external magnetic field of about 70 Gauss to induce Wiegand wire flux changes, which, in turn, generate an output pulse in the pick-up coil. Output energy of more than 3000 nJ per single pulse (open circuit) can be harvested. The output pulse is derived from the large Barkhausen effect. Therefore, the behavior of the sensor output is independent of the triggering and sensing frequencies. The objective of this review article was to comprehensively highlight research endeavors devoted to Wiegand sensors. Furthermore, application scenarios of current research results are highlighted to find potential gaps in the literature and future contributions. Perspectives and research opportunities of Wiegand sensors are proposed.

Relevant examples of the application of innovative measuring devices of NNT Company in the area of non-destructive assessment of the stress state of steel components using the Barkhausen effect are presented here. We have developed two innovative devices in which the Barkhausen effect signal detected at a given point is converted into real-time information about the stress level at that point. The research was focused on the objects and technological processes where the high stress state causes specific problems both at the stage of construction and later exploitation. Such processes include steel section manufacturing process, welding, rolling or tensile loading.

A mean-field positive-feedback (PFB) theory of ferromagnetism is used to explain the origin of Barkhausen noise (BN) and to show why it is most pronounced in the irreversible regions of the hysteresis loop. By incorporating the ABBM-Sablik model of BN into the PFB theory, we obtain analytical solutions that simultaneously describe both the major hysteresis loop and, by calculating separate expressions for the differential susceptibility in the irreversible and reversible regions, the BN power response at all points of the loop. The PFB theory depends on summing components of the applied field, in particular, the non-monotonic field-magnetization relationship characterizing hysteresis, associated with physical processes occurring in the material. The resulting physical model is then validated by detailed comparisons with measured single-peak BN data in three different steels. It also agrees with the well-known influence of a demagnetizing field on the position and shape of these peaks. The results could form the basis of a physics-based method for modeling and understanding the significance of the observed single-peak (and in multi-constituent materials, multi-peak) BN envelope responses seen in contemporary applications of BN, such as quality control in manufacturing, non-destructive testing, and monitoring the microstructural state of ferromagnetic materials. [ABSTRACT FROM AUTHOR]

The results of research of the processes of polarization of niobium-containing crystals of barium titanate in changing electric fields are presented. It has been established that the time for reorganization of the ferroelastic domain structure is 30-40 times shorter than the switching time of the total polarization of the crystal, which indicates that the main switching time of BaTiO3 : Nb5+ crystals is determined by the change in its ferroelectric 180° domain structure.

This article reviews the ferromagnetic hysteresis, magnetomechanical, and Barkhausen properties of magnetic materials and presents an integrated model to describe these effects and the underlying mechanisms that cause these effects. Hysteretic properties of ferromagnets, such as permeability, coercivity, remanence, and hysteresis loss are known to be sensitive to external factors including applied stress, temperature, and heat treatment, and internal factors like residual strain, microstructure, grain size, and anisotropy and the presence of precipitates of a second phase, such as iron carbide in steels. It thus becomes imperative to characterize the effect of these factors on the hysteresis parameters. Currently, several models such as Preisach, Stoner–Wohlfarth, and Jiles–Atherton are used to describe the magnetic hysteresis of ferromagnetic materials. We review here the quasistatic Jiles–Atherton hysteresis model which describes hysteresis in terms of domain wall motion enabling a connection to be made to the physical response of the magnetic material. This model has been extended to include the magnetomechanical effect and the Barkhausen effect in ferromagnetic materials. Theoretical work presented here provides a conceptual framework linking together these magnetic property measurements with model parameters and to the structure of the material. [ABSTRACT FROM AUTHOR]

We derive a two parameter multi-exponential model to describe the frequency spectrum of Barkhausen noise in bulk steel under high excitation rates and applied tensile stress. We show how the amplitude and shape of the frequency spectrum depend on two directly measurable quantities, Barkhausen voltage and effective magnetic permeability, respectively, and how these change with stress. By incorporating frequency and depth dependence components into our model, we provide a framework for identifying stress variations along depth, which can be used for the purposes of nondestructive characterization. [ABSTRACT FROM AUTHOR]

Thermal Barkhausen effect is observed in poly(vinylidene fluoride/trifluoroethylene) [P(VDF-TrFE)] copolymer films for the first time. Barkhausen pulses arise at phase transition close to the Curie point during both heating and cooling without an external electric field. Three types of current pulses are obtained associated with nucleation and domain wall motion. The switched dipole number under one pulse is generally much less than 1% of the sample's total dipoles. [ABSTRACT FROM AUTHOR]

Focusing on the requirements of pipeline in-line testing for stress concentration, mechanical scratches and corrosion discrimination, a numerical calculation and experimental verification study of the internal testing excitation of oil and gas pipelines based on the Barkhausen effect (magnetic Barkhausen noise (MBN)) is carried out. This paper uses finite element calculation to determine the optimal position of the sensor, quantitatively analyses the influence of parameters, such as the excitation structure size and excitation intensity, on the magnetisation field of the pipeline and obtains the optimal exciting parameters for acquiring continuous Barkhausen signals, which can provide references for designing the pipeline in-line inspection gauge for stress concentration. The feasibility of the continuous Barkhausen noise (CBN) method for long-distance pipeline stress detection is verified by simulating the operating conditions of the internal detector in the pipeline using dynamic rotating excitation. [ABSTRACT FROM AUTHOR]

This work investigates the variation in material properties of steel upon friction stir processing through its magnetic response. The steel plate of grade IS 2062 having a thickness of 3 mm have been friction stir processed (FSPed) using a tool of tungsten carbide with a 15 mm shoulder diameter along with 3 mm pin diameter with traverse of 150 mm/minute and a 800 RPM revolving speed. Magnetic response of these processed plate and base metal has been recorded using Barkhausen noise (BN) analyzer in terms of BN signal parameters i.e. the rms value and pulse count or number of pulses. Barkhausen noise analysis results have been validated with micro-hardness testing and metallographic study of as received metal and the processed samples. Higher microhardness has been found in processed sample in comparison to the as received metal due to grain refinement owing to the combined effect of plastic flow of material during stirring action of the rotating tool and the frictional heat. Barkhausen noise analysis has been performed in a wide range of magnetic field intensity (MFI) and excitation frequencies to study their effect on variation in rms value and the number of pulses. [ABSTRACT FROM AUTHOR]

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Particularly for highly stressed components, it is important to have precise knowledge of the surface and subsurface properties and, thus, of the functional properties after final grinding at the end of a complex process chain in order to avoid rejected parts. Therefore, non-destructive testing methods have been the subject of research for several years. The Barkhausen noise analysis, as a micromagnetic measuring method, has the potential to characterize the subsurface area up to an analyzing depth ff non-destructively with micromagnetic parameters. In addition to micromagnetic multiparameter approaches, which allow post-process mode clear statements about the subsurface area state, the present research work deals with the concept of a connection of a single Barkhausen noise parameter with grinding process parameters. In combination with the analytical approach of Malkin for the thermal surface and subsurface area influence, which is based on the process parameters of grinding processes, a distinction between good and rejected ground parts can be achieved. The results show that, by post-process measurements of the Barkhausen noise on case-hardened workpieces made of steel 18CrNiMo7-6 (No. 1.6587, AISI 4820) and machined by a cylindrical grinding process, incipient changes in the residual stress state up to industrial-relevant limits, which distinguish between good and rejected parts, is possible. In the future, a combination of the Malkin grinding burning limit and suffcient condition monitoring based on in-process measurements of Barkhausen noise will be investigated. The application limits of the analytical approach of Malkin as well as the measurement of the Barkhausen noise in-process have to be determined. [ABSTRACT FROM AUTHOR]

Barkhausen noise (BHN) is a voltage signal induced by a coil due to the discontinuous magnetization of ferromagnetic materials. The BHN voltage value is strongly correlated with the microstructure of such materials. In this paper, we propose a new model whereby the BHN voltage pulse width is proportional to the travel distance of the domain wall between pinning sites, and the constant of proportionality corresponds to the domain wall velocity. This correlation is examined using a model sample wherein cementite and copper precipitates as pinning sites for the domain wall were dispersed in ferrite. The test results show that the BHN voltage pulse width T and the precipitate spacing L had a proportional relationship, and that the constant of proportionality L/T grew concomitant with increases in the excitation field. The change rate of L/T with excitation field was 3.8 × 10-4 A-1 m2 sec-1, and corresponded well to the reported value that was the correlation coefficient between the domain wall velocity and the excitation field. This result demonstrates the validity of our model whereby the BHN voltage pulse is equal to the time required for the domain wall to jump over the pinning sites. [ABSTRACT FROM AUTHOR]

Magnetic Barkhausen noise (MBN) was used to characterize the progress of austenite to martensite phase transformation while cooling steel specimens, using a conventional Barkhausen noise emission setup stimulated by an alternating magnetic field. The phase transformation was also followed by electrical resistivity measurements and by optical and scanning electron microscopy. MBN measurements on a AISI D2 tool steel austenitized at 1473 K and cooled to liquid nitrogen temperature presented a clear change near 225 K during cooling, corresponding to the MS (martensite start) temperature, as confirmed by resistivity measurements. Analysis of the resulting signals suggested a novel experimental technique that measures spontaneous magnetic emission during transformation, in the absence of any external field. Spontaneous magnetic noise emission measurements were registered in situ while cooling an initially austenitic sample in liquid nitrogen, showing that local microstructural changes, corresponding to an avalanche or 'burst' phenomena, could be detected. This spontaneous magnetic emission (SME) can thus be considered a new experimental tool for the study of martensite transformations in ferrous alloys, at the same level as acoustic emission. [ABSTRACT FROM AUTHOR]

Cobalt antidot arrays defined within a Hall bar mesa have been fabricated using electron-beam lithography. The diameter of the circular antidots was fixed at 1 μm with the antidot edge-to-edge spacing varying from 2 to 0.5 μm in a square lattice and 0.4 μm in a rotated square lattice. In-plane magnetoresistance measurements were carried out to investigate the magnetization reversal properties. Antidots greatly modify the domain configuration and work as domain wall pinning sites. As a result, the switching and saturation fields increase while the magnetoresistance ratio decreases with the inclusion of antidots and also with increasing antidot areal density. Micromagnetic simulations show that the magnetization reversal of antidot arrays proceeds with the formation and annihilation of domain walls, which is manifested as Barkhausen jumps in the transition regions of the magnetoresistance curves. [ABSTRACT FROM AUTHOR]

We measured the statistical properties of Barkhausen noise in finemet films with nominal composition Fe73.5Cu1Nb3Si22.5B4 and variable thickness between 25 and 1000 nm. Films have been sputtered on glass substrates and their structure is amorphous. The critical exponents of the power-law distributions for the jumps amplitude show a remarkable stability over the whole thickness range, whereas the other macroscopic magnetic properties undergo strong variations. The value of the critical exponent is about 0.8 between 50 and 500 nm with a small increase up to 1.0 at 1000 nm. These values are similar to those observed with the same experimental technique in other two-dimensional (2D) systems, but definitely smaller with respect to the values observed in truly three-dimensional (3D) systems. Our data therefore indicate that, in the investigated thickness range, the behavior remains typical of 2D systems. The small increase of the critical exponent at 1000 nm might be an indication of a starting transition toward a 3D behavior. [ABSTRACT FROM AUTHOR]

Dual-beam high-resolution magneto-optic Kerr effect polarimetry and magnetic force microscopy (MFM) are used to study Barkhausen jumps in thin-film permalloy microstructures. Negative jumps (changes in local magnetization that oppose the drive field) are always accompanied by a nearly simultaneous positive jump, and the power-law dependence of jump-size statistical distributions of positive and negative jumps are similar. These observations, supported by sequential MFM domain images taken during field-driven reversal, indicate that negative jumps are driven by configurational changes of local domain structure associated with positive jumps that are governed by pinning, exchange, and anisotropy energies. The eddy-current coupling mechanism, that appears to account for negative jumps in bulk materials, is suppressed by sample thickness scaling in the thin-film microstructures. [ABSTRACT FROM AUTHOR]

We have performed the theoretical studies on the longitudinal dynamic magnetization process of magnetostrictive amorphous wires characterized by a large single Barkhausen jump (magnetic bistability) based on our previous experimental measurements on these wires. The domain structures of these wire samples consist of a single domain inner core with axial magnetization surrounded by the outer domain shell with the magnetization oriented perpendicular (λs>0) or circular (λs<0) to the wire axis. In the present work we use the resultant magnetization vector Mvector tilting θ angle to z axis to describe the sample’s domain structures. In terms of solving the Landau-Lifshitz-Gilbert equation followed by Mvector the analytical solution of the dimensionless axial component of the magnetization mz=MZ/Ms has been obtained, and mz[t(H0,fe),τ,γ] is a function of the field amplitude H0, field frequency fe, and the samples’ material parameters such as the damping constant τ and the gyromagnetic ratio γ. The function mz[t(H0,fe),τ,γ] allows us to study the dynamic properties of the magnetization process of a wire sample. It has been found that the switching time ts, the switching field Hsw, and the dynamic coercive field Hdc depend on a magnetic field and material parameters. We found that the parameter α=γτ/(1+τ2) related to the rate of Mvector , rotating the direction of the effective field, plays an important role in the magnetization process. By fitting the experimental data to the theoretical magnetization curve the value of the damping constant τ of the magnetostrictive amorphous wires can be estimated. [ABSTRACT FROM AUTHOR]

A detailed study of the dc hysteresis loops for current and furnace annealed amorphous wires with vanishing saturation magnetostriction constant, λs, is reported. Measurements were conducted on wires of nominal compositions (Co0.94Fe0.06)72.5Si12.5B15 and (Co0.93Fe0.07)72.5Si12.5B15 which had λs values of similar magnitude but opposite sign. The results revealed the establishment and evolution of Barkhausen jumps at different points on the major hysteresis loops. These are interpreted on the basis of the core-shell domain model, widely used in the study of amorphous magnetic wires. The control of these jumps is essential for applications of wires where magnetic noise may be an issue. The influence of annealing conditions on the coercivity and susceptibility of the wires is also reported. [ABSTRACT FROM AUTHOR]

The magnetization reversal in a thin (100 nm) Ni80Fe20/GaAs(001) film prepared by molecular-beam epitaxy has been investigated using a focused spot Kerr magnetometer. The field was sinusoidal and applied along an in-plane easy axis, with sweep rate at the coercive point in the range ∼1 kOe/s–1 MOe/s. Real time measurements of the Kerr response enabled a study of the probability distributions P(V) of the domain-wall speed as a function of sweep rate. The shape of P(V) changes from being characteristic of stochastic domain-wall motion at low sweep rate to being characteristic of quasicontinuous domain-wall motion at high sweep rate. Increasing the diameter of the focused spot from 2 to 80 μm increases the number of domain walls participating in the reversal within the probed area, which leads to an averaging effect and dulls the transition from stochastic to quasicontinuous wall motion seen in the probability distributions. [ABSTRACT FROM AUTHOR]

Evolution of Barkhausen jumps during the magnetization reversal process in disordered magnetic material is investigated. Based on the magnetoelastic effect (ΔE effect), we investigated the dynamics of Barkhausen jumps through an internal friction measurement of amorphous Fe-B-Mo ribbons. The ΔE caused by the Barkhausen jump is found to have a power-law scaling relation with the driving rate of magnetic field. Using numerical simulation, dynamics of Barkhausen avalanches in a realistic spin-lattice model for a disordered ferromagnet is analyzed. The dynamic scaling and inhomogeneous behavior observed in both experiments and theoretical models are presented and discussed. [ABSTRACT FROM AUTHOR]

Presents information on a study which investigated the origin of magnetic easy axis in pipeline steel using an angular magnetic Barkhausen noise (MBN) technique. Application of angular MBN to monitor magnetic anisotropy; Experimental technique; Results and discussion; Conclusions.

Presents information on a study on the Barkhausen noise amplitude. Mechanical stress situations with biaxial characters; Methodology used in conducting the study; Results of the study.

The paper presents the result of an analysis of applicability of various electromagnetic methods of nondestructive evaluation for creep damage detection in a novel heat resistant steel - T24 grade. Two sample sets, cut out from membrane wall tubes, were investigated – the as-delivered one and another exploited for 36,000 h in a power plant. There are described results of magnetic hysteresis loops B(H), Barkhausen noise (BN) and magnetoacoustic emission (MAE) signals measurements. Changes of the B(H) loops shape are observed mainly in the "knee" regions. The BN signal is practically unaffected by exploitation. The most strongly changing signal is the MAE signal, yet the change is not very easy to quantify as it concerns signal envelopes shape not overall intensity. The paper describes various possible signal parameters that can be used. The best one seems to be the ratio of the total pulse count for a quarter of magnetisation (demagnetisation) to the one for the magnetisation half-period. The important issue is in that case a proper choice of the threshold level in order to obtain good sensitivity to creep damage level and reasonably low stochastic pulse count scatter. • The creep damage process results in precipitates distribution modification for exploited T24 steel. • Change of microstructure strongly deteriorates material properties resulting in an increased risk of dangerous failures. • Magnetic domain walls interact strongly with carbide precipitates and as result their dynamics is affected by creep. • The most pronounced changes of B(H) loops are observed for the field ranges for which the magnetoacoustic emission peaks. • The best tool for the creep level assessment is the MAE signal, yet the analyzed signal parameters have to be well chosen. [ABSTRACT FROM AUTHOR]

A technique based on the metal magnetic memory (MMM) is developed to evaluate the contact damage of ferromagnetic materials under nonferromagnetic and ferromagnetic indenters by measuring the magnetic flux leakage (MFL) signals. Great difference between the MFL signals for the ferromagnetic indenter and non-ferromagnetic indenter is experimentally observed. The normal signal shows a dip in the contact region for the ferromagnetic indenter but an increase for the non-ferromagnetic indenter; the tangential signal experiences a peak-peak change through zero in the contact region for the ferromagnetic indenter but a peak for the non-ferromagnetic indenter. Furthermore, the amplitude of MFL signals for the ferromagnetic indenter is considerably larger than that for the non-ferromagnetic indenter. The mechanism of the signal variation is analyzed by considering the magnetic-stress coupling effect. Criteria of the early contact damage are developed based on the variations of the MFL signals and their gradients; and the evaluation parameters are extracted. [ABSTRACT FROM AUTHOR]

Highlights • A novel feature descriptor designed for BN signal of material hardness is proposed. • A new algorithm m-SFA based on multi-order SSFA signals is generated. • Discriminant incoherent component analysis was firstly employed in NDT. Abstract Barkhausen noise (BN) generated by the stochastic movements of domain walls is one of the most popular non-destructive testing signal. To measure the property of material, the feature(s) extracted from BN signal has been focused by the existing studies. Although the physical characteristic of several BN features could be proven, many features used in the BN-related works are prone to being interfered by the noise, temperature and other measurement conditions. In this paper, to build a stable and unified representation of BN signal, a novel BN feature extraction and hardness prediction method is proposed. The proposed method includes BN-reconstructed AR model, modified slow feature analysis for fusing different AR-order signal and discriminant incoherent component analysis for the hardness prediction. In the experiment, all potential parameters involved in our method were tested to show the relationship between the parameters and hardness prediction accuracy. Then our proposed method was compared with other component-analysis-based methods and self-defined isolated-feature-based prediction methods. The experimental result implies that our proposed method outperforms other methods, including features generated by component analysis methods and the combination of conventional BN features. [ABSTRACT FROM AUTHOR]

A study of the dielectric properties and the Barkhausen effect in the PMN-PT-based multicomponent ceramics near the morphotropic phase boundaries in electric fields was performed. It is shown that with an increase in electric field value (at E = 2.0–5.3 kV/cm), a plateau-like dielectric anomaly appears and a sharp suppression of the dielectric permittivity dispersion occurs. At the same range of E the Barkhausen jumps number and their intensities increase significantly. In addition, their shapes change from the first type to the second one. Possible reasons of observed experimental features in electric fields are discussed. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Domain wall dynamics in a high magnetostrictive Fe-Co alloy wire (λ s = 102 ppm) was evaluated by magnetic Barkhausen noise (MBN) technique. • Stress effect on MBN profiles and the frequency analysis were investigated by using a tensile test machine. • The stress dependence of the root mean square (RMS) of the MBN signals shows a good sensitivity (0.038 mV/MPa). Abstract Magnetic Barkhausen noise (MBN) plays significant roles to describe the dynamic of domain walls (DWs), but an in-depth understanding of the correlation between Barkhausen effect and magnetostrictive effect during magnetization process is still limited. In this study, we investigated MBN signals and the frequency spectra in a high-magnetostrictive Fe 30 Co 70 alloy wire (λ s = 102 ppm) by evaluating the stress effects on MBN profiles at the stress range of 0–150 MPa using tensile test machine. The results from MBN profiles revealed that MBN in the high magnetic field region was responsible for the localized changes of magnetic flux density, d B /d t induced by magnetic distortion related to non-180° DWs or the magnetization rotation. In MBN spectra, the peak shift towards lower frequencies with the increase of stress indicates that the rough pulse-like MBN outbreaks increase, and it results mainly from the increase of DW jumping length which is caused by the pinning effect at grain boundaries where DW energy is relatively high. In addition, stress dependence of the root mean square (RMS) value of MBN showed a good sensitivity (0.038 mV/MPa). Overall, these findings indicate that new MBN measurement system utilizing magnetostrictive materials can be helpful for a wide range of applications such as mechanical stress sensors and energy harvester systems. [ABSTRACT FROM AUTHOR]

• Presents a new system for the estimation of the stress in pipelines using MBN. • Proposes the parameters of MBN to estimate the stress amplitude and direction. • Proposes a model for the dependence of MBN on the applied stress. In the present work a new system for nondestructive evaluation of applied stress on the pipeline steels surface is proposed. This system is based on applying a magnetic field on the pipe surface, whose direction changes due to rotatory permanent magnets. The variation of magnetic field direction produces the Barkhausen signal, which is measured by a pick-up coil. The angular dependence of the magnetic Barkhausen noise signal energy is influenced by the pipe surface curvature due to the changing head-probe liftoff. Also, the said angular dependence changes with the applied tensile stress due to the magneto-elastic effect. The result of Barkhausen noise measurements in the pipeline surface submitted to applied tensile stress reveals that, since the effect of curvature on the angular dependence remains constant, the effect of applied stress could be determined by analyzing the angular dependence variation of the Barkhausen signal with the applied stress. [ABSTRACT FROM AUTHOR]

Abstract This paper reports the non-destructive evaluation of railway wheels via the Barkhausen noise technique across the wheel width. This study correlates non-destructive Barkhausen noise parameters with conventional destructive analyses expressed in terms of metallographic and SEM observations, microhardness profiles, residual stress, and average grain size measurements. The condition of the wheel surface was altered remarkably due to the real and long-term wheel operation. The results of investigations indicate non-homogenous distribution of Barkhausen noise emission as well as the corresponding surface state with respect to the wheel width. Severe plastic deformation and superimposed elevated temperatures alter the grain size considerably in the near-surface as well as the subsurface region. It was found that Barkhausen noise is strongly correlated with the average grain size within the Barkhausen noise sensitive depth, whereas the correlation with the residual stress distribution is quite poor. Highlights • Barkhausen noise emission is sensitive to the rail wheel damage. • Barkhausen noise emission is driven by grain refinement. • Wheel surface damage is asymmetrical with respect to the wheel width. [ABSTRACT FROM AUTHOR]

Abstract We report the crossover of Barkhausen noise statistics upon a change in the measurement geometry. The behaviour is akin to the angle dependent critical to sub-critical crossover of avalanche statistics as present in avalanche models with random anisotropy directions. The samples studied were 15–25 nm thin films of iron, grown on (001) GaAs by pulsed laser ablation. Use of planar Hall effect as a probe for the magnetic state facilitated this work, which would be impractical to do in a MOKE setup. We compare our data with simulations of a random anisotropy Ising model, and demonstrate striking similarity between experimental and simulated avalanche size distributions. Further, through micromagnetic simulations, we conclude that crystallite misorientations were the origin of domain wall pinning in our system leading to Barkhausen noise. Highlights • Barkhausen avalanches in a magnetically 2D thin film studied by planar Hall effect. • Sub-critical statistics observed with in-plane magnetic field. • Statistics change to critical when field tilted out of plane. • Explanation through random anisotropy Ising model. • Micromagnetic simulations indicate nature of disorder. [ABSTRACT FROM AUTHOR]

A non-destructive characterisation method for the prediction of mechanical properties using the magnetic Barkhausen noise (MBN) technique has been introduced. The study found that there are monotonous changing trends between the changing feature values of MBN signals and the mechanical properties of cold-rolled strips. A back-propagation (BP) neural network model was established to simultaneously predict three mechanical property parameters, with the thickness of samples and feature values of MBN signals as input values and the yield strength, ultimate tensile strength and elongation as output values. The results showed that the neural network model has a high degree of accuracy and generalisation ability to obtain accurate values of mechanical properties. Furthermore, the estimated relative errors of the three mechanical property parameters of cold-rolled strips using a single non-destructive testing (NDT) method are less than 7%. [ABSTRACT FROM AUTHOR]

This paper deals with the non destructive evaluation of components after the plasma nitridation via the Barkhausen noise techniques. Effect of different surface states before the plasma nitriding is studied via the non destructive Barkhausen noise technique, as well as the conventional destructive techniques. Bending of flat samples to different bending angles was performed and magnetic, as well as conventional destructive testing, was carried out on the outer, inner and flat surfaces. The results of experiments show that the Barkhausen noise emission is a function of the heat treatment, whereas intensity of bending and the corresponding deformation are only minor. The different states of the surface before the plasma nitriding result into the similar thickness of the compound layer. Furthermore, the underlying diffusion of near the surface layer state is different. [ABSTRACT FROM AUTHOR]

The design, fabrication, and characterization of a 4.08 mm2 monolithic 82-GHz silicon impact ionization avalanche transit time (IMPATT) transmitter are presented. The vertical IMPATT diode was grown by molecular beam epitaxy and followed by the typical circuit fabrication process. The oscillator design is experimentally well verified both by the Kurokawa condition from impedance matching and by Barkhausen’s criteria from the reflection coefficient aspect, respectively. An 82.5-GHz coplanar waveguide (CPW) patch antenna with 50- $\Omega $ input impedance is monolithically integrated to an IMPATT oscillator with similar working frequency. Under the biasing condition of 25 mA (13.41 V), the $H$ -plane radiation pattern of the monolithic IMPATT transmitter was characterized at 82.17 GHz in an E-band anechoic chamber. From link budget calculation, the equivalent isotropically radiated power of the transmitter chip achieved 18.43 dBm (69.66 mW). With the simulated directive gain (7.35 dBi) of CPW patch antenna and measured CPW interconnect loss (0.57 dB), the output power of transmitter achieved 11.65 dBm (14.62 mW) with dc-to-radio frequency efficiency of 4.36%. [ABSTRACT FROM AUTHOR]

The paper presents the results of application of a novel Barkhausen effect (BE) probe with adjustable magnetizing field direction for the stress level evaluation in ferromagnetic materials. The investigated sample was in a form of a pipe, made of P91 steel that was anisotropic due to the production process. The measurements were performed before and after welding, revealing the influence of welding process on the residual stress distribution. As was observed, the process introduced high tensile stresses in the normal to the weld direction (which can be interpreted as a decrease of strongly compressive residual stresses present in martensitic steels). In addition to that, the paper presents investigations of the measurement set performance corroborating its applicability for Barkhausen effect signal measurements in the magnetically anisotropic materials. The signals obtained during manual rotation of the probe (typical method of BE measurements) are very similar to those recorded during automatic field axis rotation. [ABSTRACT FROM AUTHOR]

Abstract Steel samples cut from two line pipes with unknown processing history were analyzed using magnetic Barkhausen noise (MBN), electron backscatter diffraction (EBSD) and Vickers hardness techniques on the pipe surface and on sections through the wall thickness. The results show that the MBN responses vary significantly not only between the two pipe steels, but also among different thickness layers of each steel. Both steels show considerable variations in MBN at different locations on the surfaces. For one steel, the surface MBN illustrates an inverse linear relationship with respect to the hardness, while the other does not depict such a relation since the variation in hardness at different locations is very small. Across the thickness, the microstructure (phase and grain size) of both steels is quite similar, but the texture shows significant differences. Again, there is a large difference in hardness across the thickness for one steel, while the other only shows very small variation in hardness across the thickness. The variations in average MBN across the wall thickness for both steels are quite large. Angular MBN measurements on the sectioned samples revealed significant discrepancies in the magnetic anisotropy in the two steels. Based on the analysis of the angular MBN data with respect to the single and dual easy axis models, one pipe can be determined to have been manufactured through a seam welding process, while the other may have been formed by spiral welding. Due to the residual stresses in the steel samples, the effect of the crystallographic texture on the anisotropy in MBN response has essentially been suppressed. Highlights • The hardness, microstructure, texture and MBN of two pipeline steels were analyzed. • The angular MBN results revealed possible manufacturing histories of the two pipelines. • The MBN is closely related to the processing history, microstructure and stress state. • The use of MBN technique can help address the integrity issues in the pipeline industry. [ABSTRACT FROM AUTHOR]

Non-oriented electrical steels are indispensable materials for use in electric motors as magnetic cores. It is desired that the magnetic properties of the steel sheets be optimal and uniform in all the directions in the sheet plane. Thus, knowing the magnetic properties of the steel sheets in all the directions is crucial for the design of the motors. However, the magnetic properties of non-oriented electrical steels are usually measured by the standard Epstein frame method, which normally only gives the overall magnetic properties in the rolling and transverse directions and those in other directions are usually unknown. In this paper, magnetic Barkhausen noise (MBN) analysis is utilized to characterize the local magnetic response of non-oriented electrical steel. By aligning the MBN sensor to all the directions in the sheet plane, angular magnetic response is obtained. The measured MBN is then directly compared to the texture factor evaluated in the same direction. In this way, the local magnetic response of the steel is correlated with the crystallographic texture. It was found that MBN technique was able to detect the difference in magnetic response induced by magnetocrystalline anisotropy if the effect of the residual stress can be eliminated. This would provide a potential technique for the characterization of magnetic properties of non-oriented electrical steel. [ABSTRACT FROM AUTHOR]

Post-treatment and rescaling is made possible to plot local hysteresis cycles from the measurement of local magnetic Barkhausen noise (BN). If the material is homogeneous and if similar excitation conditions are imposed, the local hysteresis cycles obtained are comparable to the classical magnetic hysteresis cycles $B(H)$ (the cross section magnetic average induction $B$ as a function of the surface tangential excitation field $H$). These local BN hysteresis cycles provide interesting clues about the evolution of the microstructure of the magnetic material (internal stresses, level of degradation, etc.). This makes it an interesting tool for the non-destructive evaluation of ferromagnetic steels. In this paper, a phenomenological modeling of the BN from the local modeling of $B$ subjected to an excitation field $H$ and/or a uniaxial mechanical stress $T$ is proposed. The final objective is to provide an absolute quantification of the internal residual stresses from the BN measurements. [ABSTRACT FROM AUTHOR]