Magnetic force microscope

MFM scanning often uses non-contact atomic force microscopy (NC-AFM) and is considered to be non-destructive with respect to the test sample.

In MFM measurements, the magnetic force between the test sample and the tip can be expressed as [1][2] where

The cantilever tip flies above the sample with a typical distance of tens of nanometers.

For small deflections, the tip-cantilever can be modeled as a damped harmonic oscillator with an effective mass (m) in [kg], an ideal spring constant (k) in [N/m], and a damper (D) in [N·s/m].

[16] If an external oscillating force Fz is applied to the cantilever, then the tip will be displaced by an amount z.

That is, the shift in the resonance frequency is a result of changes in the spring constant due to the (repelling and attraction) forces acting on the tip.

) of the sample in the presence of the applied magnetic field of the tip (whichever is easier).

Then, integrate the (dot) product of the magnetization and stray field over the interaction volume (

MFM images of various materials can be seen in the following books and journal publications:[5][6][19] thin films, nanoparticles, nanowires, permalloy disks, and recording media.

Housing of the MFM system is important to shield electromagnetic noise (Faraday cage), acoustic noise (anti-vibration tables), air flow (air isolation), and static charge on the sample.

Wu et al., have used a tip with antiferromagnetically coupled magnetic layers in an attempt to produce a dipole only at the apex.

MFM images of 3.2 Gb and 30 Gb computer hard-drive surfaces.
Comparison of Faraday-effect image (left) and MFM image (inset, lower-right) of a magnetic film
Typical atomic force microscopy set-up
Typical atomic force microscopy set-up