Variable Field Module™

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For researchers that want to apply a magnetic field to their samples, Asylum Research has developed a small sample Variable Field Module (VFM™) for the MFP-3D™ System. This module is useful for MFM, conductance, and other applications where the sample has a dependence on the applied magnetic field. The VFM applies an in-plane field exceeding ± 2,500 Oe with <1 Oe resolution.

The VFM easily fits on the MFP-3D (Figure 1.) The VFM features adjustable pole tips that allow the maximum value of the applied field to be increased or decreased. This module uses a unique design incorporating rare earth magnets to produce the magnetic field so there is no heating or drift as the field changes.

Image Examples
Figure 2 shows a series of MFM images rendered in ARgyle™ of an Iomega Zip® disk in an applied magnetic field. Bits are visible in the lower red image and then are erased in the 650 Oe blue image. There is still a great deal of roughness visible in the saturating 1500 Oe field magenta image. The scans were taken with a high coercivity (ASYHCMFM) cantilever with the VFM, erasing the magnetic data.

Figure 3 shows two MFM images of VHS tape. The top image shows the topography. The middle shows the MFM image with no magnetic field applied. Data written onto the tape appears as alternating dark and bright bands. The bottom image shows the MFM data after a 1400 Gauss, in-plane field was applied from right to left with the VFM, erasing the magnetic data. The images were taken with an MFP-3D Stand Alone System and Asylum Research ASYMFMHC high coercivity cantilevers.

Figure 4 shows a QuickTime® movie of magnetic nanoparticles in the presence of an applied, in-plane magnetic field using the VFM. First, the sample was saturated at -2000 Oe. The imaging began at 0 Oe with a
maximum field of +1000 Oe applied.

Features
• Unlike electromagnets, the VFM uses rare earth magnets that mean no unwanted heating or drift in your images. The VFM can remain at its
maximum field indefinitely.

• Adjustable pole pieces allow the maximum field intensity to be varied.

• ±2,500 Oe standard. Please contact Asylum Research if you have other requirements.

• Field intensity is software controllable. An integrated Gaussmeter provides a quantitative measure of the applied magnetic field.

•Includes a beryllium copper, non-magnetic cantilever clip that prevents magnetic field distortion.

VFM module shown in its storage module.

Figure 1: The Variable Field Module is shown mounted on the MFP-3D scanner. The magnetic field is easily adjusted through the software interface.

Figure 3: Top image: Topography of VHS tape, 80µm scan. Middle: MFM image of data tracks written onto VHS tape at 0 Oe. Bottom: At 1400 Oe, the VHS tracks have been erased. The applied field direction is right to left.

Figure 4: QuickTime movie of paramagnetic nanoparticles on a mica substrate as a magnetic field is being applied. Sample courtesy G. Agarwal lab, Ohio State University.