Scanning SQUID microscopy – a powerful tool for quantitative microscale magnetic imaging
ORAL
Abstract
Nowadays, material science requires precise quantitative microscale measurements of magnetic materials. A Superconducting Quantum Interference Device (SQUID) is the most sensitive detector of magnetic fields available and can be constructed with sub-micrometer dimensions via lithography. A scanning SQUID microscope (SSM) uses a specialized SQUID sensor to image weak local magnetic fields with micrometer spatial resolution. Local susceptibility can be measured using a one-turn field coil integrated into the SQUID sensor to apply a localized magnetic field. We can also reconstruct the 2D current density in the sample from the magnetic flux image above the sample. Three imaging modes are then available: magnetometry, susceptometry, and current imaging. In the NSF funded service center for SSM at Stanford University, magnetic fields of nano Tesla and dipole moments of hundreds of Bohr magnetons are detectable in magnetometry, as well as a volume susceptibility of 10-7 in susceptibility mode and a current of nano amps in current sensing mode. By maintaining thermal separation between the sample and the SQUID sensor, the sample temperature can be varied between 4.3 K and 110 K while scanning. A wide variety of applications of SSM would be included in this talk.
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Presenters
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Huiyuan Man
Geballe Laboratory for Advanced Materials, Stanford University, Johns Hopkins University, Department of Physics and Astronomy, Johns Hopkins University, Stanford University
Authors
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Huiyuan Man
Geballe Laboratory for Advanced Materials, Stanford University, Johns Hopkins University, Department of Physics and Astronomy, Johns Hopkins University, Stanford University
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John Robert Kirtley
Geballe Laboratory for Advanced Materials, Stanford University
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Kathryn Ann Moler
Stanford Univ, Department of Applied Physics and Physics, Stanford University, Department of Applied Physics, Stanford University