THE BARKHAUSEN EFFECT: NEW PERSPECTIVES
FOR AN OLD PROBLEM
G. Durin
Istituto Elettrotecnico Nazionale Galileo Ferraris and GNSM, C.so
Massimo d’Azeglio 42, I-10125 Torino, Italy
The recent developments of the research on the Barkhausen noise and on nature of the magnetization process are reviewed. After a few comments on the experimental setups for reliable measurements, a tentative classification of the Barkhausen effect properties is presented. The relationship between the existing theories, still to be refined, and the recent studies about the self-organized criticality of complex systems and the surface growth models is analyzed, showing the new appealing theoretical perspectives recently appeared in the literature.
DEPENDENCE OF BARKHAUSEN REPRODUCIBILITY
ON HYSTERESIS LOOP SIZE
J. R. Petta and M. B. Weissman, G. Durin*
Department of Physics, University of Illinois at Urbana-Champaign,
1110 West Green Street, Urbana, Il 61801-3080
* Istituto Elettrotecnico Nazionale Galileo Ferraris and INFM,
C.so Massimo d'Azeglio, 42 I - 10125 Torino Italy
The Barkhausen pattern from the amorphous alloy Fe21Co64B15 showed high sweep-to-sweep reproducibility for most sweeps when driven slowly over a minor hysteresis loop. Small changes in the maximum applied field led to completely different pulse patterns. When driven near saturation the sweep-to-sweep reproducibility was lost. Large features observed on rapid sweeps were also reproducible, but not when the sample was driven to fields about two orders of magnitude larger than the coercive field.
NEW ELEMENTS FOR A THEORY OF THE BARKHAUSEN
EFFECT
G. Durin, P. Cizeau*, S. Zapperi*, and H.E. Stanley*
Istituto Elettrotecnico Nazionale Galileo Ferraris and INFM, C.so
Massimo d’Azeglio 42, I-10125, Torino, Italy
* Center for Polymer Studies and Dep. of Physics, Boston University,
Boston, Massachusetts 02215
We present a microscopical model of the domain wall motion through a disordered medium. Unlike a previous phenomenological model, which explains most of the experimental data, the disorder is supposed to be uncorrelated. The dynamical equation of the motion has a upper critical dimension of 3, so that a mean field description is suitable to describe soft magnetic materials. It is shown that the correlation of the disorder is a consequence of the nature of the magnetic interactions and not an intrinsic property of the materials. The mean field critical exponents well agree with the phenomenological model and with simulated and experimental data.
DETERMINATION OF BARKHAUSEN SIGNAL
SCALING FROM HIGHER ORDER SPECTRAL ANALYSIS
J. R. Petta and M. B. Weissman, and G. Durin*
Department of Physics, University of Illinois at Urbana-Champaign,
1110 West Green Street, Urbana, Illinois 61801-3080
* Istituto Elettrotecnico Nazionale Galileo Ferraris and INFM,
Corso Massimo d'Azeglio 42, I- 10125 Torino, Italy
Third and fourth order spectral measurements of Barkhausen noise in polycrystaline FeSi (3% Si) and previously measured Fe21Co64B15 samples showed striking differences. FeSi spectral measurements were consistent with independent pulse models, unlike data from amorphous Fe21Co64B15. Second spectral data for FeSi yields a valid relationship between the pulse height and duration. Our measurements indicate that the variability of the high frequency exponent, which experimentally ranges between 1.5 and 2, is due to effects dependent upon the domain structure and other inherent properties of the material.
EFFECT OF STRESS ANISOTROPY ON
HYSTERESIS AND BARKHAUSEN NOISE IN AMORPHOUS MATERIALS
C. Appino, G. Durin, V. Basso, C. Beatrice, M. Pasquale, and G.
Bertotti
IEN Galileo Ferraris and INFM, C.so M. D’Azeglio 42, 10125
Torino, Italy
Hysteresis, power losses, and the Barkhausen effect are investigated in an Fe-based highly magnetostrictive amorphous material, as a function of applied stress. By means of the static and dynamic Preisach model, and of existing theories of the Barkhausen effect, the results are shown to be compatible with the existence of a characteristic structural length \delta_c, playing a role similar to that of grain size in crystalline materials. At low applied stresses, where the magnetization process is dominated by quenched-in stresses \sigma_i, \delta_c is identified with the typical wavelength of \sigma_i fluctuations. The theoretical analysis leads to the estimate \delta_c ~ 70-100 \mu m and <\sigma_i> ~ 3.5 MPa.
CONNECTION BETWEEN HYSTERESIS, BARKHAUSEN NOISE, AND MICROSTRUCTURE IN MAGNETIC MATERIALS
G. Durin, C. Beatrice, C. Appino, V. Basso, and G. Bertotti
Istituto Elettrotecnico Nazionale Galileo Ferraris and INFM, Corso
M. d’Azeglio 42,
I-10125 Torino, Italy
The interplay between material microstructure and magnetic hysteresis
is studied in rapidly
quenched Si–Fe alloys. Two ribbons of different average grain
dimension <s> ~35 and 160 mm! were prepared by annealing
at different temperatures and studied through two independent
approaches: Barkhausen noise measurements, and Preisach analysis
of static and dynamic hysteresis loops. In order to monitor the
effect of demagnetizing fields on the magnetization process, the
strips were progressively shortened from 30 to 10 cm. The correlation
length of a domain-wall jump was estimated through the analysis
of Barkhausen jump distributions versus apparent permeability.
The correlation length of the coherent magnetization reversals
controlling excess dynamic losses was estimated through the Preisach
analysis of dynamic hysteresis loops. In the sample with lower
<s>, both the Barkhausen and the dynamic loss correlation
lengths are comparable to <s>, showing that a single structural
feature governs all aspects of magnetization reversal. Conversely,
in the high s& sample, the ribbon thickness competes with
<s> in controlling static and dynamic magnetization processes.
UNIVERSALITY AND SIZE EFFECT
IN THE BARKHAUSEN NOISE
Gianfranco Durin and Stefano Zapperi
We show that the Barkhausen avalanches exhibit power law distributions and scaling exponents belonging to two distinct universality classes. We explain these results in terms of the critical behavior of the domain wall at the depinning transition, with exponents set by the long-range dipolar interactions arising from local magnetostatic fields, and by the elastic curvature of the wall. We are also able to predict the precise dependence of the cutoff on the demagnetizing factor $k$ due to sample size. These predictions are experimentally confirmed on three samples (two polycrystalline 6.5 \% wt. Si-Fe and an amorphous Fe$_{21}$Co$_{64}$B$_{15}$ under applied tensile stress) which are progressively cut in order to increase $k$. All these results allow to link the material microstructure and the sample geometry to the macroscopic noise properties.