Magnetic Force (MFM) Imaging
MFM Using Interleave Scanning and LiftMode
228
MultiMode SPM Instruction Manual
Rev. B
for all TappingMode-capable microscopes in the form of Digital Instruments Veeco’s Basic
Extender Electronics Module (Basic Extender) and Quadrex Extender Electronics Module
(Quadrex Extender). (Microscopes without an Extender addition cannot utilize phase detection; for
more information, contact Veeco.) The design of the NanoScope IV integrates the Quadrex
Extender. Phase detection and frequency modulation detection are superior methods for magnetic
force imaging, offering greater ease of use, better signal-to-noise ratios, and reduced artifact
content as compared to amplitude detection. Extender electronics are strongly recommended for
extensive MFM imaging.
13.2.1 Procedure
1. Mount a magnetic-coated probe on the scanner or tip holder. The tip should be magnetized
with a strong permanent magnet before installing the tip holder on the AFM head. Tips are
usually magnetized with the field aligned along the tip axis (perpendicular to the sample
surface). The MFM then senses force gradients due to the perpendicular component of the
samples’s stray field. Tip magnetizers can be purchased from Veeco.
2. Set up the AFM as usual for TappingMode operation. In all
Channel
panels, the
Highpass
and
Lowpass
filters should be
Off
. Set the
Rounding
parameter in the
Microscope
>
Calibrate
>
Scanner
window to zero (
0.00
).
3. The procedure to tune the cantilever drive frequency and amplitude depends on whether you
are using phase detection or amplitude detection. Both cases rely on automatic
Cantilever
tune
just as when preparing for TappingMode; see
manual. MFM cantilevers typically have resonant frequencies between 50 and100kHz. If
using the
AutoTune
feature, these values can be used as bounds for the frequency sweep.
With the Extender option, two curves appear in the
Cantilever Tune
box: the
amplitude
curve in white, and the
phase
Basic Extender Module display only the amplitude curve.
•
Setting a Drive Frequency for Phase Detection
: The
Drive frequency
should be set
to the center of the cantilever resonance, as shown in
. This will be done
automatically if using
AutoTune
.
Figure 13.2a
Cantilever Tune
for phase detection and frequency modulation
035
