Mapping of magnetic stray field distribution over the surface of a sample in MFM require probes with magnetic coating. The probe is sharp enough to image magnetic domains on surface.

The Co-Cr coating on most MFM probes creates a magnetic moment of about 10-13 emu. Imaging in external magnetic field is a way to enhance the sensitivity further as it may increase the moment of both the MFM tip and the sample. Note that the magnetic structure of some samples having low coercivity (permalloy, garnet films, etc.) may be significantly affected by the magnetized Co-Cr coated probe.

Though the Cr provides a protection for cobalt from oxidizing, magnetic probes have a limited shelf life that ranges from weeks to months and depends mostly on humidity. However, there may be other reasons why probes lose sensitivity. Sometimes, magnetization with an arbitrary stong magnet may help to restore the probes, e.g. SmCo or NdFeB.

Height and phase images of the magnetic dipoles obtained using Co-Cr cantilevers. The structure is formed in a layer of Fe0.7C0.3 by annealing with interfering laser impulses . Images are courtesy of Prof. Sheviakov (MIET, Moscow).


co-cr coated probes
The magnetic Co-Cr coating is a Co layer on the tipside of the cantilever, which is protected from oxidation by a thin Cr film. The resulting curvature radius of the tip is below 90 nm.
  • 8 nm
  • 8 nm
  • < 60 nm
  • 40°
  • 12 - 18 µm
  • n-type silicon
  • 0.01 - 0.025 Ohm*cm
  • Magnetic
  • Aluminum


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Probes with magnetic coating for MFM.