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(above) The goal of magnetic resonance force microscopy (MRFM) is to
produce 3-dimensional,
non-destructive, in-situ, atomic-resolution images of atoms, molecules, defects in solids,
dopants in semiconductors, and binding sites in viruses. In a typical setup, shown above,
a thin silicon cantilever is poised above a tiny sample containing, say, a virus to be imaged.
A magnetic particle mounted on the cantilever interacts (under the additional influence of fields
from an RF coil) with tiny volumes of magnetic atoms in the sample. Under just the right
circumstances the particle on the cantilever (like a diver on a diving board) will begin to
resonantly oscillate; the cantilever's movement shifts a laser interference pattern viewed
through an optical fiber. The magnetic force (only atto-Newtons, or 10-18 Newtons, in strength) measured
in this way will be used to gain information about individual atoms in the sample. The
sample can be scanned under the probe and the measurements repeated.
(above) A closeup of an MRFM probe and a nearby molecule
whose structure is to be imaged. The pink bowl-shaped surface represents
(as in conventional nuclear magnetic resonance imaging) the volume of space
where magnetic atoms can be in resonant interaction with the probe; atoms closer
to the probe will feel too-strong a force, while atoms further away will feel too weak a force.
After further development of MRFM technology, the thickness of the resonant volume will
be less than one angstrom, far better than for present MRI imaging.
This research was described at the American Physical Society March Meeting,
17-21 March 1997, in Kansas City, Missouri.
