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A scanning Hall probe microscope for high resolution magnetic imaging down to 300 mK
V V Khotkevych1, M V Milosević, S J Bending
1Department of Physics, University of Bath, Claverton Down, BA2 7AY Bath, United Kingdom.
The Review of Scientific Instruments
|January 7, 2009
Summary
We developed a low-temperature scanning Hall probe microscope for high-resolution magnetic imaging. This instrument maps magnetic fields with submicron precision, visualizing phenomena like superconducting vortices and magnetic domains.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- Accurate characterization of magnetic materials at the nanoscale is crucial for developing advanced electronic and spintronic devices.
- Existing techniques often face limitations in resolution, scanning range, or operating temperature.
- The need for versatile microscopy capable of probing magnetic phenomena under diverse conditions is paramount.
Purpose of the Study:
- To design, construct, and evaluate a novel low-temperature scanning Hall probe microscope.
- To achieve submicron lateral resolution and a large scanning range for detailed magnetic imaging.
- To enable simultaneous acquisition of Hall and scanning tunneling microscopy (STM) signals.
Main Methods:
- Integration of a Hall probe sensor with an STM tip within a detachable microscope head.
- Operation within a commercial 3He-refrigerator, covering temperatures from room temperature down to 300 mK.
- Utilizing a three-axis slip-stick nanopositioner for precise in situ probe positioning within a 6x6x7 mm³ volume.
- Employing microfabricated Hall sensors (e.g., GaAs/AlGaAs, AlGaAs/InGaAs/GaAs) for magnetic induction mapping.
- Sensing and controlling tunnel currents for close proximity of the Hall probe to the sample surface.
Main Results:
- Demonstrated submicron lateral resolution in magnetic field mapping.
- Achieved minimum detectable fields greater than or equal to 10 mG/Hz(1/2).
- Successfully imaged superconducting vortices in a Nb thin film at 372 mK.
- Captured labyrinth magnetic-domain patterns in an yttrium iron garnet film at room temperature.
- Enabled simultaneous tunneling and Hall signal acquisition in surface-tracking mode.
Conclusions:
- The developed low-temperature scanning Hall probe microscope offers a powerful tool for nanoscale magnetic characterization.
- The system's versatility allows for the study of diverse magnetic phenomena across a wide temperature range.
- Its high resolution and sensitivity pave the way for advancements in condensed matter physics and materials science research.
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