Power Spectrum Of Barkhausen Noise Research Articles

Noise in disordered systems: The power spectrum and dynamic exponents in avalanche models

For a long time, it has been known that the power spectrum of Barkhausen noise had a power-law decay at high frequencies. Up to now, the theoretical predictions for this decay have been incorrect, or have only applied to a small set of models. In this paper, we describe a careful derivation of the power spectrum exponent in avalanche models, and in particular, in variations of the zero-temperature random-field Ising model. We find that the naive exponent, $(3\ensuremath{-}\ensuremath{\tau})/\ensuremath{\sigma}\ensuremath{\nu}z,$ which has been derived in several other papers, is in general incorrect for small $\ensuremath{\tau},$ when large avalanches are common. $(\ensuremath{\tau}$ is the exponent describing the distribution of avalanche sizes, and $\ensuremath{\sigma}\ensuremath{\nu}z$ is the exponent describing the relationship between avalanche size and avalanche duration.) We find that for a large class of avalanche models, including several models of Barkhausen noise, the correct exponent for $\ensuremath{\tau}<2$ is $1/\ensuremath{\sigma}\ensuremath{\nu}z.$ We explicitly derive the mean-field exponent of $2.$ In the process, we calculate the average avalanche shape for avalanches of fixed duration and scaling forms for a number of physical properties.

The effect of hydrogenation on the magnetization reversal process in amorphous ferromagnets

The influence of hydrogenation and dehydrogenation on the power spectra of Barkhausen noise in amorphous alloys has been investigated. It has been shown that after hydrogenation local stress centers occur in amorphous structure. Presence of the centers leads to long-wave fluctuations of domain wall energy which cause the decrease of the number of irreversible domain wall displacements.

The effect of neutron irradiation on the Barkhausen noise in amorphous Fe40Ni40B40 alloys

Theoretical expression for the power spectra of Barkhausen noise was used to obtain information on the dynamical properties of domain walls from the experimental spectra. It was shown that after irradiation the domain wall mobility increases due to the change of the effective mass of domain wallsmef, damping constantβ and the spring constantα.

Coercivity and power spectrum of Barkhausen noise in structural steels

Relative coercivities and power spectra of Barkhausen noise are measured for ferritic pearlitic C-Mn, tempered microalloyed and 9% Ni steels under unstressed and tensile stressed conditions. Coercivity depends on the type of material, stress state, amounts of pearlite and grain boundary precipitates, grain size and dislocation density. The stress dependence of coercivity is extremely strong in the Ni steel, relatively strong in the tempered steel at low stress levels and small in the ferritic-pearlitic steels. The power spectra exhibit clustering in elementary magnetic transitions, which can be expressed in terms of the mean pulse duration ϱ τ 0. This is inversely proportional to coercivity, incrasing as a function of grain size D approximately as D 1 2 . Tensile stress directed parallel to the magnetization prolongs ϱ τ 0 in the case of the ferritic- pearlitic and tempered steels but shortens it in the case of the Ni steel. The stress dependence of ϱ τ 0 and noise level are controlled by possible grain boundary phases and the amount of pearlite (lamellar carbides). Grain boundaries and lamellar precipitates tend to suppress displacements of the 90° domain walls, which increases the stress response of the noise at high stress level.

Contribution to the theory of the Barkhausen power spectra of amorphous ferromagnets

The influence of the finite velocity of domain wall on the shape of the power spectra of Barkhausen noise is analysed. It is shown that the power spectrum is significantly influenced by the dynamical properties of domain walls.

Power Spectrum of the Barkhausen Noise of Various Magnetic Materials

This work describes a simple apparatus used to measure power spectra of Barkhausen noise in an analysis frequency band between 25 and 104 cps. Because previous work by the authors showed that when the specimen is in the form of a closed magnetic circuit and unlaminated the intensity of the noise has but small dependence on the core dimensions, unlaminated ring-shaped samples were used in this work. Spectra obtained with a magnetizing field frequency of 0.1 cps are given for iron, 6% silicon iron, grain-oriented silicon iron, ultraperm, mumental, nickel, and Permalloy C. It is observed that the intensity of the noise depends to a large extent on the nature of the ferromagnetic material. No interpretation of this fact is given, as it appears very complicated to understand.