Barkhausen noise and size effects in magnetic microstructures

Callegaro, Luca; Puppin, E.; Ricci, S.

doi:10.1063/1.1388023

Cited by 8 publications

(5 citation statements)

References 27 publications

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“…7 The sample used in the BE experiments reported in this paper exhibited the same typical low static coercivity ͑ϳ0.5 Oe͒ and simple domain patterns common to thin-film permalloy microstructures. 7,13 III. RESULTS AND DISCUSSION Figure 1 displays representative measured changes in magnetization produced by BJs during field-driven magnetization reversal of the microstructured sample.…”

Section: Methodsmentioning

confidence: 99%

Domain wall dynamics and Barkhausen jumps in thin-film permalloy microstructures

Yang

Erskine

2005

Phys. Rev. B

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Domain wall jump-amplitude and velocity distributions associated with Barkhausen jumps in a 300-Å-thick thin-film permalloy and a 200ϫ 200 ͑m͒ 2 ϫ 220-Å-thick permalloy sample microstructrue are measured using a high-speed magneto-optic Kerr effect polarimeter. The jump-amplitude and velocity distributions are obtained for applied-field sweep rates from 0.9 Oe/ s to 6.3ϫ 10 4 Oe/ s. The velocity distributions exhibit statistical properties consistent with the stochastic description of field-driven domain wall motion developed by ABBM ͓B. Alessandro, C. Beatrice, G. Bertotti, and A. Montorsi, J. Appl. Phys. 68, 2901 ͑1990͔͒. Averaged velocity distributions exhibit the expected increase of dynamic coercivity as the sweep rate is increased, and the maximum domain wall velocity measured as a function of the applied field at the stochastic depinning threshold is shown to be governed by the mobility limit imposed by local spin damping. The averaged velocity ͗͑H − H 0 ͒͘ obtained from the distributions is observed to depart from the commonly accepted lineardependence model, especially at higher drive-field sweep rates. This departure is interpreted as an indication of a sweep-rate-dependent mobility. Sweep-rate-dependent jump-amplitude distributions P͑⌬M͒ versus ⌬M are obtained from the Barkhausen effect data. These distributions exhibit power-law behavior with a sharp cutoff at large values of ⌬M. Attempts to reconcile the measured jump-amplitude distributions and sweep-ratedependent exponents with various models of universal scaling are described. Power-law fits to P͑⌬M͒ distributions measured to optimize temporal resolution ͑required for the velocity-distribution studies͒ yield a sweeprate-dependent exponent that varies from ␤ = 1.45± 0.05 to ␤ = 1.0 as dH / dt is varied from 25 Oe/ s to 6.3 ϫ 10 4 Oe/ s. This range of sweep-rate-dependent ␤ agrees with the ABBM model and is consistent with the sweep-rate dependence exponent rule that predicts linear sweep-rate scaling for the adiabatic value ␤ =3/2 ͓R. A. White and K. A. Dahmen, Phys. Rev. Lett. 91, 085702 ͑2003͔͒. Additional experiments on both 300-Å-thick continuous films and the same microstructures optimized for ⌬M sensitivity yield a more accurate value of ␤ ͑␤ = 1.33± 0.01͒, which corresponds to a CZDS model ͑␤ =4/3͒ ͓C. Cizeau, S. Zapperi, G. Durin, and H. E. Stanley, Phys. Rev. Lett. 79, 4669 ͑1997͒; Phys. Rev. B 58, 6353 ͑1998͔͒. Adiabatic limit values of ␤ determined from all of the experiments are definitively outside the range ␤ ϳ 1.0 for self-organized criticality in a two-dimensional system ͓P. Bak, C. Tang, and K. Wiesenfeld, Phys. Rev. Lett. 59, 381 ͑1987͔͒, and also appear to be inconsistent with experimental results for 900 Å Fe films on MgO in which ␤ = 1.1 was obtained from rescaled P͑⌬M͒ distributions ͓E. Puppin, Phys. Rev. Lett. 84, 5415 ͑2000͔͒. The sweep-rate dependence of ␤ determined in a system that manifests an adiabatic limit of ␤ that is not equal to 3 / 2 also violates the model of White and Dahman that prohibits sweep-rate-dependent s...

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Section: Methodsmentioning

confidence: 99%

Domain wall dynamics and Barkhausen jumps in thin-film permalloy microstructures

Yang

Erskine

2005

Phys. Rev. B

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“…The presence of reproducible plateaux is observed everywhere over the sample surface, although the number and position of the magnetization states are related to the particular region investigated. In fact, the existence of these states can also be found on other samples with a different composition and size [9,10].…”

Section: Resultsmentioning

confidence: 69%

Section: Resultsmentioning

confidence: 75%

“…It is apparent that magnetization is not a smooth function of the applied field, but evolves through magnetization plateaux and Barkhausen jumps. This feature is not related to the particular sample investigated, but has been observed in different continuous or structured ferromagnetic films, when either the spot size, or the overall sample dimension, are sufficiently small[7][8][9].In figure1are also illustrated the physical quantities measured by the analysis program: the jump with index k, taking place at the applied magnetic field H (k), carries the system from a magnetization state M(k − 1) to the final state M(k), and has an amplitudeM(k) = M(k) − M(k − 1). After this jump, the state M(k) is maintained until a new jump with index k + 1 occurs; the state M(k) has the corresponding width H (k) = H (k + 1) − H (k).The statistical distribution of the jump height M, the Barkhausen 'amplitude' probability distribution indicated as p M , shows critical behaviour and has been the subject of much experimental and theoretical work[2]; the technique described in section 2 permitted us to study p M on thin films and magnetic structures.…”

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confidence: 76%

“…A new technique, based on magneto-optical ellipsometry with a focused laser beam [6], permits the detection of Barkhausen jumps in thin films and particles [7][8][9][10]. In thin films, the spatial resolution obtained is sufficient to isolate and follow the magnetization of a small portion of the whole sample.…”

Section: Introductionmentioning

confidence: 99%

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Barkhausen jumps and metastability

Callegaro¹,

Puppin²,

Zani³

2003

J. Phys. D: Appl. Phys.

Self Cite

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The magnetization process drives a ferromagnetic system through a sequence of discrete metastable magnetization states; the abrupt transitions taking place between these states are responsible for the Barkhausen noise. In thin films, the magnetization states of a small region of the sample surface can be identified, and experimental information can be gained on the statistical properties of the magnetization sequence. Here we investigate the stability of the system in a particular state in the presence of an increasing magnetic field, which we call the state life. A simple statistical model, based on the reliability theory, is proposed in order to explain the observed data.

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Carbon Encapsulation of High Entropy Alloy Nanoparticles with Extraordinary Coercivity and Saturation at Room Temperature

Tseng

Chi

Tsai

et al. 2020

Part & Part Syst Charact

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Owing to their unique properties and technological potential, high entropy alloys (HEAs) have become the subject of great interest in the materials science community. HEAs consist of more than four principle elements in equimolar ratio so their configurational entropy is intrinsically greater than one‐principle element based. The increasing surface energy and chemical tendency toward clustering of like atoms at low dimension, however, make production of HEA‐nanoparticles (HEA‐NPs) extremely difficult. A facile production of HEA‐NPs inside carbon nanotubes and nanoparticles is demonstrated in this work. Electron microscopic and elemental analyses confirm encapsulated to be solution phase; some embrace carbides and form multidomains with chemical composition ranging from quaternary to quinary phase. Multidomains and nonmagnetic centers create hardening thus promoting coercivity significantly at room temperature. Alloying induces electron redistribution into high spin states, accounting for observed high saturation. Configurational entropy of encapsulated HEA‐NPs lies on a range comparable with bulk.

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Barkhausen noise and size effects in magnetic microstructures

Cited by 8 publications

References 27 publications

Domain wall dynamics and Barkhausen jumps in thin-film permalloy microstructures

Domain wall dynamics and Barkhausen jumps in thin-film permalloy microstructures

Barkhausen jumps and metastability

Carbon Encapsulation of High Entropy Alloy Nanoparticles with Extraordinary Coercivity and Saturation at Room Temperature

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