Domain Wall Motion

Understanding how domain walls move in a magnetic material while being driven by an applied magnetic field is a problem common to many magnetic devices such as: transformers, magnetic recording read/write heads, and various other magnetic sensors. We are investigating the potential use of SEMPA for imaging domain motion with the ultimate goal of imaging of domain wall dynamics at frequencies up to 1 MHz.

As a first step we have used SEMPA to image the magnetic domain structure of METGLAS^® amorphous ferromagnetic ribbons produced by AlliedSignal Inc. The ribbons are used as magnetic core material in power distribution transformers and the domain motion is of great importance in determining their energy efficiency. The figure shows SEMPA images of the magnetic domains under four static applied fields. The central hysteresis loop, which was recorded under ac excitation, illustrates the magnetic state corresponding to each image. The small, relatively immobile domains at the upper right of the images are pinned by a surface defect.

Next, we are looking at various stroboscopic imaging schemes in order to image the domains while being driven by a time dependent, periodic applied magnetic field. A natural application of such an instrument would be the dynamic domain imaging of sub-micron GMR devices, such as MRAM's, sensors and magnetic read heads.

John Unguris
Robert J. Celotta
Daniel T. Pierce

Andrew Gavrin - Indiana University-Purdue University at Indiana
Michael Kelley - NIST
David Tulchinsky - Naval Research Laboratory

Anatol Rabinkin - Allied Signal

Supported in part by the Office of Naval Research

Online: May 1996
Last Updated: February 2008

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