Measures magnetic force gradient distribution
above the sample surface; performed using LiftMode
(see below) to track topography (Extender Electronics
Module recommended). The tip is oscillated 10's
to 100's of nm above the surface and gradients
in the magnetic forces on the tip shift the resonant
frequency of the cantilever. Monitoring this shift,
or related changes in oscillation amplitude or
phase, produces a magnetic force image. MFM provide
useful information about magnetic information
for storage media (disks, tapes), magnets and
soft magnetic materials
MFM boasts many capabilities that complement existing
imaging methods. Resolution is routinely better
than 50 nm far surpassing that of optical techniques
(such as Kerr microscopy). Also, sensitivity is
sufficient to image individual sub micron particles.
Fields can be imaged through the nonmagnetic and
opaque overcoats often applied to hard disks and
magneto-optical media. Compared to electron-based
scanning methods (i.e., Lorenz microscopy and
SEMPA), MFM offers convenience and ease of use.
Imaging is done under ambient conditions, it requires
little or no sample preparation, and results are
obtained in a few minutes. With its dual identity
as a magnetic and atomic force microscope, an
MFM instrument can also characterize media topography
(such as hard-disk roughness) with sub-angstrom
vertical resolution.
User Manual
for Magnetic Force Microscopy
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