AFM

Asylum Research
Variable Field Module Allows Study of Samples
Under Either In-Plane or Out-of-Plane Magnetic Fields
Introduction
The Variable Field Module (VFM4) is an accessory forAsylum Research Jupiter XR atomic force microscopes(AFMs) that enables researchers to apply an adjustable
magnetic field either in-plane with the sample or out-ofplane while simultaneously making AFM measurements(Figure 1). Though most often used in conjunction withmagnetic force microscopy (MFM), the VFM4 may also beused with techniques such as conductive AFM (CAFM), todirectly measure nanoscale magnetoresistance, and on
diverse samples including piezoelectric and ferroelectricmaterials. No other commercial solution offers the same
capabilities, versatility, and ease of use for magnetics
research.

Figure 1: VFM4 Variable Field Module
The VFM4 is a small stage that easily mounts to the accessory
chuck of Jupiter XR. The photo shows it in the in-plane field
configuration.

Applying In-Plane Magnetic Fields
Figure 2 shows a diagram of the VFM4 configured forin-plane magnetic fields. For highest field strength (up to±8000 G) and best field uniformity, small, thin samples areused and placed directly between the two removable polepieces.

• Applied field: 0 G• Applied field: 2500 G

Figure 3 demonstrates the effect of an increasing magnetic
field on bits written to a piece of PMR (perpendicularmagnetic recording) hard disk. The bits are progressively
degaussed as the in-plane magnetic field is increased fromzero to > 5700 G.
Removablepole piece

SampleSensorSoft iron(gray parts)

Removablepole piece• Applied field: 4160 G • Applied field: 5670 G

Rotating
permanentmagnet

H=0 G; θ=0˚

H=8000 G; θ=90˚

Figure 2: Schematic of in-plane field configuration
The strength and sign of the magnetic field applied to the sample
depends on the rotation angle of the rare earth magnet. At 0° or180°, the magnetic flux is shunted away from the sample by thesoft iron armature and pole pieces. As the magnet rotates, moreand more flux is coupled instead through the sample. At 90,° thefield is maximized.

Figure 3: Degaussing bits on PMR hard drive
Four MFM images showing a piece of PMR hard disk that iseventually degaussed when the in-plane magnetic field reachedabove 5700 G.

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Applying Out-of-Plane Magnetic Fields
Figure 4 shows how the removable pole pieces of the VFM4
allow it to be reconfigured for out-of-plane magnetic fields.
The flux lines are sketched in an idealized way here, but
in reality, the longer, less direct path necessitated byplacement of the AFM head above the sample reduces themaximum achievable field to ±1200 G.
Application Note, “Magnetic Force Microscopy Under
Applied Perpendicular Fields with Asylum Research AFMs,”
can be found online at: http://AFM.oxinst.com/OOP-MFM

Removablepole piece

SampleSensorposition

Removablepole piece

Rotating
permanentmagnet

Soft iron(gray parts)

Figure 5: VFM accessory on Jupiter XR
VFM accessory is shown mounted on the accessory chuck thatis attached to the XY scanner of the Jupiter XR.

Features and Benefits• Easily configurable for applying both in-plane andout-of-plane magnetic fields

H=0 G; θ=0˚• Unique design uses a permanent magnet, eliminating thelarge thermal drift caused by field generators that useelectromagnets.

• Field strength adjustment is motorized and can becontrolled using linear ramps.

• Integrated Hall sensor measures the in-plane fieldstrength, while an external Gaussmeter is provided formeasuring the out-of-plane field strength.

VFM4 Specifications• Field directions: Includes both in-plane and out-of-planecapabilities, easily reconfigured by the user

• Maximum field: ±8000 G in-plane• Maximum field ±1200 G out-of-plane (±1500 G typ.)• Environmental controls: Ambient only (no heating, cooling,or closed cell available concurrent with VFM)

H=1200 G; θ=90˚
Figure 4: Schematic of out-of-plane field configuration
The out-of-plane configuration works with the same principles as
the in‑plane configuration, except that the sample is placed on
one pole of the iron armature, well-separated from the other pole,such that the flux lines run through the plane of the sample. Bothconfigurations place the sensor at a position symmetric in thefield relative to the sample to avoid a positional offset error and toachieve better accuracy.

Think the VFM4 might be helpful
to your research? Let’s talk!
Email: AFM.info@oxinst.com, orCall: +1-805-696-6466

The foregoing brochure is copyrighted by Oxford Instruments Asylum Research, Inc. Oxford Instruments Asylum Research, Inc.
does not intend the brochure or any part thereof to form part of any order or contract or regarded as a representation relating
to the products or service concerned, but it may, with acknowledgement to Oxford Instruments Asylum Research, Inc., be used,applied or reproduced for any purpose. Oxford Instruments Asylum Research, Inc. reserves the right to alter, without notice thespecification, design or conditions of supply of any product or service. Datasheet #39 – 3/2021.

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Web: http://AFM.oxinst.com
Email: AFM.info@oxinst.com

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