Negative Barkhausen jumps in permalloy thin-film microstructures

Abstract

Dual-beam high-resolution magneto-optic Kerr effect polarimetry and magnetic force microscopy ͑MFM͒ are used to study Barkhausen jumps in thin-film permalloy microstructures. Negative jumps ͑changes in local magnetization that oppose the drive field͒ are always accompanied by a nearly simultaneous positive jump, and the power-law dependence of jump-size statistical distributions of positive and negative jumps are similar. These observations, supported by sequential MFM domain images taken during field-driven reversal, indicate that negative jumps are driven by configurational changes of local domain structure associated with positive jumps that are governed by pinning, exchange, and anisotropy energies. The eddy-current coupling mechanism, that appears to account for negative jumps in bulk materials, is suppressed by sample thickness scaling in the thin-film microstructures.

Computer Simulations on Barkhausen Effects and Magnetizations in Fe Nano-Structure Systems

“…The calculated ΔH B nicely fit with the experimental data. 9) These numerical simulations in §3 clearly show the general magnetization characteristics such as the magnetization curves, the B effects and the ΔH B distributions, which also coincide with the experimental data in good agreements. 9)-13)…”

“…The observation of negative Barkhausen jumps is reported in ref. 9) with permalloy thin-film microstructures as a violent case.…”

Topological electromotive force from domain-wall dynamics in a ferromagnet

“…structures. [42][43][44] Each vortex DW is characterized by two integers p the polarization and q the vorticity. p = Ϯ 1 indicates whether n in the vortex core is pointing upward or downward and q = Ϯ 1 is the winding number of n around the vortex core.…”

Outlook of Preisach Modeling and Magnetic Non Destructive Testing

“…Monte Carlo simulations have shown that the negative susceptibility around zero field is indeed associated to dislocations because of spin fluctuations [3]. Finally, negative Barkhausen jumps may be possible if the increase in the local Zeeman energy is associated with a local magnetic configuration with the magnetization opposing the applied field [11]. Concluding, the vector Preisach model proposed is promising for use with magnetic NDT techniques while the role of the differential permeability in magnetic NDT needs to be further investigated.…”