Domain-wall dynamics and Barkhausen effect in metallic ferromagnetic materials. II. Experiments

Alessandro, B.; Beatrice, C.; Bertotti, G.; Montorsi, Arianna

doi:10.1063/1.346424

Cited by 160 publications

(108 citation statements)

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“…The irreversible, nonlinear, and time-dependent response of the magnetization to an external magnetic field is traced as a time-or frequency-dependent open loop, which represents the sequence of metastable states occupied by the magnet as it adapts its domain configuration to the external field. Magnetic noise associated with the loop was first heard by Barkhausen in 1919, when he detected irreversible domain wall movement in nickel wires via the emf generated in a pickup coil by the flux jumps [1,2]. Barkhausen noise provides the basis for a method of nondestructive testing of steel parts under ac excitation [3].…”

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Magnetic Noise in Structured Hard Magnets

et al. 2010

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The anomalous Hall effect of wires patterned from ðCo 90 Fe 10 =PtÞ n multilayers, with 10 n 50, is used to determine the magnetization process in a small volume of maze domains. Time-independent 1=f noise appears in samples with a quality factor Q < 1 at points on the hysteresis loop where the magnetization reverses continuously. The magnetic noise is associated with reversible excursions of segments of a domain wall $100 nm long. Barkhausen jumps are observed close to either the switching field or the saturation field where the noise power spectrum varies as 1=f 1:7 , and its magnitude decays with time. DOI: 10.1103/PhysRevLett.104.047202 PACS numbers: 75.60.Ej, 75.75.Àc, 75.50.Ww, 85.75.Nn Hysteresis is the defining property of a ferromagnet. The irreversible, nonlinear, and time-dependent response of the magnetization to an external magnetic field is traced as a time-or frequency-dependent open loop, which represents the sequence of metastable states occupied by the magnet as it adapts its domain configuration to the external field. Magnetic noise associated with the loop was first heard by Barkhausen in 1919, when he detected irreversible domain wall movement in nickel wires via the emf generated in a pickup coil by the flux jumps [1,2]. Barkhausen noise provides the basis for a method of nondestructive testing of steel parts under ac excitation [3]. It has been used to study correlations in magnetization reversal cascades by recording the jumps with a magneto-optical microscope [4].Single-domain particles of hard magnets may exhibit coherent magnetization reversal-the classical StonerWohlfarth behavior [5]-when they are about 10 nm in size, or less [6]. Uniformly magnetized films of similar thickness having spontaneous magnetization M and perpendicular anisotropy K u exhibit perpendicular magnetization when the quality factor Q ¼ 2K u = 0 M 2 is greater than 1. The hysteresis may then be a simple square loop like that of a Stoner-Wohlfarth particle, with an abrupt switch from magnetization þM to ÀM at the coercive field H c , when the applied field is along the easy axis. Perpendicular magnetization remains possible when Q < 1, but in a multidomain state, which is stabilized by the stray field created by a maze of stripe domains. The magnetization switches from a uniformly magnetized state in a positive applied field to a maze domain state, which is then progressively demagnetized by domain wall motion. The reverse stripes broaden and the normal stripes narrow before breaking up into segments and bubbles, and eventually disappear as the sample reaches saturation in the reverse direction [7,8]. Thin film multilayers of Fe or Co and Pt or Pd with perpendicular magnetization are of great interest for magnetoelectronics, magnetic recording and studies of the physics of magnetic interactions at the nanoscale level. In this Letter, we show how the magnetic noise due to fluctuations in the magnetization of a small sample volume changes as we go around the hysteresis loop. The fluctuations are measured using t...

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Magnetic Noise in Structured Hard Magnets

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“…The grain sizes in the "B", C", and "D" samples are comparable and thus it is difficult to distinguish the peak positions for these samples. The accuracy in the determination of the peak position is generally poor, as was described in [23]. As a consequence, the quantitative assessment of the dependence between the grain size and the peak position is a hard task.…”

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“…As a consequence, the quantitative assessment of the dependence between the grain size and the peak position is a hard task. Next, the dependence of the maximum of the spectrum F m on the correlation length [23] can be written as…”

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“…This shift of the peak frequency with the grain size is in agreement with the model described in [22], where the correlation length parameter ξ of the model, which represents the range of interaction of domain walls with pinning sites, was found to be proportional to the grain size. The dependence of the peak position f m on the correlation length can be obtained from the ABBM model [23] in the form…”

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Investigation of Two-Stage Magnetic Barkhausen Noise Measurement Method at Power Line Frequency

Pal’a

Šoka

2016

Acta Phys. Pol. A

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The aim of the paper was to study the features of measurement of the magnetic Barkhausen noise by the new two-stage method in the high excitation frequency region (power line frequency). The magnetic Barkhausen noise was investigated on grain oriented Fe-3%Si steel subjected to different heat treatment. By application of an air coil on the output of the power amplifier we were able to linearize the excitation field. At the same time, the air coil suppressed the unwanted noise from the output of the power amplifier. We have found that the two-stage method is able to reveal a peak of the power spectrum even if it is located at low frequency, in contrast to the classical one-stage method. Further, we successfully applied a model of the power spectrum to the real magnetic Barkhausen noise obtained from the two-stage measurement.

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“…[1][2][3][4][5][6][7][8][9][10] This type of behaviour is a result of Brownian correlations in the pinning potential and can be quantified by power-law functions. These dynamics are also reflected in the power spectrum of Barkhausen emissions, which, at the lower end scales as approximately 1=x 2 in the Alessandro-BeatriceBertotti-Montorsi (ABBM) model 11,12 and from 1=x 1:3 to 1=x 2 in the Random Field Ising (RFI) model, depending on the strength of dipolar interactions. 1,13 The regions in which scale invariance applies, widen when the material is driven at a low field rate, below a critical driving velocity.…”

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A model for the Barkhausen frequency spectrum as a function of applied stress

Kypris

Nlebedim

Jiles

2014

Journal of Applied Physics

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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 non-destructive characterization. KeywordsBarkhausen effects, Domain walls, Emission spectra, Elasticity, Random Noise Disciplines Electromagnetics and Photonics CommentsThe following article appeared in Journal of Applied Physics 115 (2014) 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. V C 2014 AIP Publishing LLC. [http://dx

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Domain-wall dynamics and Barkhausen effect in metallic ferromagnetic materials. II. Experiments

Cited by 160 publications

References 15 publications

Magnetic Noise in Structured Hard Magnets

Magnetic Noise in Structured Hard Magnets

Investigation of Two-Stage Magnetic Barkhausen Noise Measurement Method at Power Line Frequency

A model for the Barkhausen frequency spectrum as a function of applied stress

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