Quantitative Magneto-Mechanical Detection and Control of the Barkhausen Effect

Science  01 Mar 2013:
Vol. 339, Issue 6123, pp. 1051-1054
DOI: 10.1126/science.1231390

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Controlling Magnetic Noise

Ferromagnetic materials contain a number of magnetic domains, with individual domains switching stochastically as the field strength is increased. As magnetic memory elements shrink in size, it is important to understand, and ultimately control, this magnetic noise. Using a magnetic vortex core integrated with a nanomechanical torsion balance, Burgess et al. (p. 1051, published online 17 January) created a two-dimensional map of the magnetic potential within the sample with nanoscale resolution. Moreover, introducing geometric defects (dimples) in the sample allowed the magnetization to be stabilized.


Quantitative characterization of intrinsic and artificial defects in ferromagnetic structures is critical to future magnetic storage based on vortices or domain walls moving through nanostructured devices. Using torsional magnetometry, we observe finite size modifications to the Barkhausen effect in the limiting case of a single vortex core interacting with individual pointlike pinning sites in a magnetic thin film. The Barkhausen effect in this limit becomes a quantitative two-dimensional nanoscale probe of local energetics in the film. Tailoring the pinning potential using single-point focused ion beam implantation demonstrates control of the effect and points the way to integrated magneto-mechanical devices incorporating quantum pinning effects.

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