Statistics of the pinning field in a soft metallic ferromagnet

The demagnetization curve, or initial magnetization curve, is studied by examining the embedded Barkhausen noise using the non-equilibrium, zero temperature random-field Ising model. The demagnetization curve is found to reflect the critical point seen as the system's disorder is changed. Critical scaling is found for avalanche sizes and the size and number of spanning avalanches. The critical exponents are derived from those related to the saturation loop and subloops. Finally, the behavior in the presence of long range demagnetizing fields is discussed. Results are presented for simulations of up to one million spins.

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“…Mills and M. B. Weissman using a soft magnetic material suggest the results of Fig. 4 are correct [18].…”

Section: Relationmentioning

confidence: 77%

Barkhausen noise and critical scaling in the demagnetization curve

Carpenter

Dahmen

2003

Phys. Rev. B

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“…where β is a damping constant, I s is the saturation magnetization, c H t is the external field increasing at rate c H , −kx is the demagnetizing field and W (x) is a random field with Gaussian distribution and Brownian correlations [20]. These correlations are believed to represent an effective description of a more general model with flexible domain walls [21,22].…”

mentioning

confidence: 99%

“…The equation of motion for the wall position x is given by where β is a damping constant, I s is the saturation magnetization, c H t is the external field increasing at rate c H , −kx is the demagnetizing field and W(x) is a random field with gaussian distribution and brownian correlations 20 . These correlations are believed to represent an effective description of a more general model with flexible domain walls 21,22 . Equation (2) can be solved exactly and provides an excellent description of the statistical properties of the Barkhausen noise, considering that the domainwall velocityẋ is proportional to the recorded v(t).…”

mentioning

confidence: 99%

Signature of effective mass in crackling-noise asymmetry

et al. 2005

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C rackling noise is a common feature in many dynamic systems 1-9 , the most familiar instance of which is the sound made by a sheet of paper when crumpled into a ball. Although seemingly random, this noise contains fundamental information about the properties of the system in which it occurs. One potential source of such information lies in the asymmetric shape of noise pulses emitted by a diverse range of noisy systems [8][9][10][11][12] , but the cause of this asymmetry has lacked explanation 1 . Here we show that the leftward asymmetry observed in the Barkhausen effect 2 -the noise generated by the jerky motion of domain walls as they interact with impurities in a soft magnet-is a direct consequence of a magnetic domain wall's negative effective mass. As well as providing a means of determining domain-wall effective mass from a magnet's Barkhausen noise, our work suggests an inertial explanation for the origin of avalanche asymmetries in crackling-noise phenomena more generally.Crackling noise is the response of many physical systems to a slow external driving force, characterized by outbursts of activity (avalanches or pulses) spanning a broad range of sizes, separated by quiescent intervals 1 . In condensed matter, notable examples are the magnetization noise emitted along the hysteresis loop in ferromagnets (that is, the Barkhausen effect 2 ), the noise from magnetic vortices in type-II superconductors 3 , ferroelectric materials 4 and driven ionic crystals 5 . In the context of mechanics, examples are the acoustic emission signal in fracture 6 and plasticity 7 and, on a larger scale, seismic activity corresponding to an earthquake 8,9 . Quantitative understanding of crackling noise is of fundamental importance in different applications, from non-destructive material testing to hazard prediction. This goal can be achieved only through the identification of general universal properties common to these systems, irrespective of their differences in the internal dynamics and microstructural details. In this context, the average shape of the individual pulses of which the signal is composed has been proposed as the best tool to characterize these universal features of crackling noise 1 . In analogy with critical phenomena, it is expected that pulses of different durations can be rescaled on a universal function, whose shape would only depend on general features of the physical process underlying the noise. This scenario is supported by the analysis of a variety of models, where pulse shapes are described by universal symmetric scaling functions [12][13][14] . In most experimental data, however, the pulse shape is markedly asymmetric with respect to its midpoint, that is, avalanches start quickly but return to zero more slowly 1,[8][9][10][11][12] . These results are puzzling because the models accurately reproduce several other universal quantities, such as avalanche distributions and power spectra 11,15 .One of the most studied examples of crackling noise is the Barkhausen effect recorded in soft magnetic mate...

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“…Alternatively, Néel [26] and other authors [27, 28] used the 'DW energy gradient' to express the DW contributions to the linear and quadratic Rayleigh terms. The influence of the internal stresses on the DW stability is sometimes discussed in terms of a 'restoring pressure' [29], or a 'random pinning field' [30][31][32]. Hrianca [12] examined the motion of a 90 • DW when activated by the stress.…”

Section: Introductionmentioning

confidence: 99%

Magnetomechanical damping in stress-relieved Ni: the effect of the dc magnetic field

Ercuţa¹

2008

J. Phys.: Condens. Matter

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The effect of the dc magnetic field on the damping behaviour of a stress-relieved Ni sample is examined under low frequency free torsional vibrations. High damping capacity, reaching 40% fractional energy dissipation per full period was detected in stages of high magnetization, beyond 90% from technical saturation. The damping of magnetic origin is attributed to the vibration-induced movement of the still existing non-180 • domain walls, through the irregular energy landscape generated by their interaction with the structure defects. The overall energy loss per full period of vibration is evaluated as the statistical addition of contributions from local dissipative processes consisting in forward and reverse Barkhausen jumps, triggered by the periodic stress and either favoured or suppressed by the field, depending on its strength. Predictions were obtained in good agreement with the experiment.

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Statistics of the pinning field in a soft metallic ferromagnet

Cited by 5 publications

References 17 publications

Barkhausen noise and critical scaling in the demagnetization curve

Barkhausen noise and critical scaling in the demagnetization curve

Signature of effective mass in crackling-noise asymmetry

Magnetomechanical damping in stress-relieved Ni: the effect of the dc magnetic field

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