COLUMBUS, Ohio -- What is there to see inside a magnet that's smaller than the head of a pin?
Quite a lot, say physicists who've invented a new kind of MRI technique to do just that.
The technique may eventually enable the development of extremely small computers, and even give doctors a new tool for studying the plaques in blood vessels that play a role in diseases such as heart disease.
In a recent issue of Physical Review Letters, the scientists report the first-ever magnetic resonance image of the inside of an extremely tiny magnet.
Specifically, the magnet is a "ferromagnet" -- a magnet made of ferrous metal such as iron. It's what most people think of when they hear the word "magnet."
"The magnets we study are basically the same as a refrigerator magnet, only much smaller," said project leader Chris Hammel, Ohio Eminent Scholar in Experimental Physics at Ohio State University. The disk-shaped magnets in this study measured only two micrometers (millionths of a meter) across.
"Because ferromagnets generate such strong magnetic fields, we can't study them with typical MRI. A related technique, ferromagnetic resonance, or FMR, would work, but it's not sensitive enough to study individual magnets that are this small."
Likewise, medical researchers can't use MRI to image plaques formed in the body, because plaques are too small. That's why this new kind of magnetic resonance could eventually become a tool for biomedical research.
The technique combines three different kinds of technology: MRI, FMR, and atomic force microscopy.
They dubbed the technique "scanned probe ferromagnetic resonance force microscopy," or scanned probe FMRFM, and it involves detecting a magnetic signal using a tiny silicon bar with an even tinier magnetic probe on its tip.
As the probe passes over a material, it captures a bowl-shaped image: a curved cross-section of an object. The magnetic
|Contact: P. Chris Hammel|
Ohio State University