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Magnetic Force Microscopy

Advanced MFM Operation

Rev. D Dimension 3100 Manual 267

Setpoint

For the most reproducible results, it is best to use a consistent setpoint. In LiftMode, the total tip-

sample distance h

tot

is the sum of the average tip-sample distance in TappingMode h

, and the lift

scan height h

lift

(see Figure 15.3b). In TappingMode, the average tip-sample distance h

is equal to

the oscillation amplitude, which is determined by the setpoint and the amplitude sensitivity of the

tip. MESPs typically have an amplitude sensitivity of approximately 25nm/V.

Large variations in setpoint can change the total tip-sample distance in LiftMode, sometimes with

visible results in the magnetic image. For this reason, reproducible results are most easily obtained

by using consistent setpoints. Note that a lift scan height of 0nm still gives a mean tip-sample

distance of h

in LiftMode.

Figure 15.3b Tip Height and Oscillation Amplitudes (TappingMode & LiftMode)

The relationship between setpoint voltage and oscillation amplitude is known as the sensitivity. Its

value can be determined with Force Calibration (see Chapter 13). For 225µm MFM cantilevers,

the sensitivity is typically in the range 20-25nm/V. The exact value depends on the position of the

laser spot on the cantilever, the cantilever geometry, and the particular instrument. A 1V Setpoint

typically corresponds to h

~14-18nm.

tot

+ h

lift

Lift Pass

TappingMode Pass

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