In the race to develop the next generation of storage and recording media, a major hurdle has been the difficulty of studying the tiny magnetic structures that will serve as their building blocks. Now a team of physicists at the University of California, Davis, has developed a technique to capture the magnetic “fingerprints” of certain nanostructures — even when they are buried within the boards and junctions of an electronic device.

Due to the miniscule physical dimensions of nanomagnets — some are as small as 50 atoms wide — observing their magnetic configurations has been a challenge, especially when they are not exposed but built into a functioning device.

To tackle this challenge, Liu and three of his students, Jared Wong, Peter Greene and Randy Dumas, created copper nanowires embedded with magnetic cobalt nanodisks. Then they applied a series of magnetic fields to the wires and measured the responses from the nanodisks. By starting each cycle at full saturation — that is, using a field strong
enough to align all the nanomagnets — then applying a progressively more negative field with each reversal, they created a series of information-rich graphic patterns known to physicists as “first-order reversal curve (FORC) distributions.”

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