Magnetic microscopy using SQUIDs

Wellstood, F. C.; Gim, Y.; Amar, A.; Black, R. C.; Mathai, A.

doi:10.1109/77.621996

Cited by 32 publications

(9 citation statements)

References 16 publications

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“…The resolution of SQUID microscopes is currently limited to about 5 m by the size of the inner hole. 242,243 While SQUIDs have been primarily used for dc magnetic measurements, it is also possible to apply them for ac. Black et al 244 have shown that it is possible to perform eddy current microscopy with these probes when applying a driving current at 26 -100 kHz.…”

Section: Magnetic Field Probes and Microwave Squidsmentioning

confidence: 99%

High-frequency near-field microscopy

Rosner

Weide

2002

Review of Scientific Instruments

219

133

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Conventional optics in the radio frequency ͑rf͒ through far-infrared ͑FIR͒ regime cannot resolve microscopic features since resolution in the far field is limited by wavelength. With the advent of near-field microscopy, rf and FIR microscopy have gained more attention because of their many applications including material characterization and integrated circuit testing. We provide a brief historical review of how near-field microscopy has developed, including a review of visible and infrared near-field microscopy in the context of our main theme, the principles and applications of near-field microscopy using millimeter to micrometer electromagnetic waves. We discuss and compare aspects of the remarkably wide range of different near-field techniques, which range from scattering type to aperture to waveguide structures.

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Section: Magnetic Field Probes and Microwave Squidsmentioning

confidence: 99%

High-frequency near-field microscopy

Rosner

Weide

2002

Review of Scientific Instruments

219

133

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“…Scanning SQUIDs have been used to image the magnetic fields from a wide variety of sources, ranging from the developmental currents generated by the embryo in a chicken egg to the persistent currents associated with quantized flux in superconductors. The interested reader is referred to previous reviews for more details on the history of this microscope, on experimental considerations, and on applications to, for example, biology and biomedicine (13)(14)(15)(16)(17)(18). In this review, we outline the most important features of SQUID microscopy, the design considerations that make SQUID microscopes well-suited for particular materials science applications, and discuss in detail several measurements of interest to the materials science community.…”

Section: Squid Microscopesmentioning

confidence: 99%

“…Ten years ago, the resolution limit for room temperature samples was achieved with a four-channel SQUID whose 3-mm diameter pickup coils are 1.5 mm from room temperature and have a noise of 100 fT/ √ Hz (36). Within the last five years, the great advance in resolution was achieved by the Maryland group, which developed an HTS SSM that is 40 µm from a room temperature sample (16), provides 50-µm spatial resolution, but has 34 pT/ √ Hz noise at 100 Hz and 260 pT/ √ Hz at 1 Hz (bias switching should improve the low-frequency performance); a commercial version of this instrument provides a sensitivity of 20 pT/ √ Hz, an unenhanced spatial resolution of 50 µm, and the ability to detect for a wire 100 µm from the SQUID currents as low as 10 nA with a 1-s averaging time (37). Lee et al have fabricated an inverted HTS system designed for biological measurements (31,32) that uses a 3-µm thick silicon nitride window so that the separation between the 40 µm SQUID and the room-temperature sample is as low as 15 µm.…”

Section: Scanning Squid Microscopesmentioning

confidence: 99%

“…The capabilities of systems with cryogenic samples is even more impressive. SQUID microscopes have been demonstrated with a spatial resolution as fine as 4 µm for samples that are in the same cryogenic environment as the SQUID sensor (14,16,(38)(39)(40)(41)(42)(43)(44). Systems with both the sample and the SQUID immersed in liquid helium have 66 µm resolution and 5.2 pT/ √ Hz noise at 6 kHz (42), and 10 µm at 100 pT/ √ Hz (43); the Conductus Scanning Magnetic Microscope TM provided micron resolution for helium-temperature samples (38).…”

Section: Scanning Squid Microscopesmentioning

confidence: 99%

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Scanning Squid Microscopy

Kirtley¹,

Wikswo

1999

Annu. Rev. Mater. Sci.

161

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The scanning SQUID microscope (SSM) is a powerful tool for imaging magnetic fields above sample surfaces. It has the advantage of high sensitivity and bandwidth and the disadvantages of relatively modest spatial resolution and the requirement of a cooled SQUID sensor. We describe the various implementations of this type of instrument and discuss a number of applications, including magnetic imaging of short circuits in integrated circuits, corrosion currents in aluminum, and trapped flux in superconductors.

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“…High-T c SQUIDs are also used in scanning, but their sensitivity is about an order of magnitude worse than for low-T c SQUIDs with equivalent spatial resolution (Wellstood et al 1997). The smallest SQUIDs reported to date were fabricated by Hasselbach et al (2000) from…”

Section: Chapter 1 Introductionmentioning

confidence: 99%

Scanning Hall Probe Microscopy of Magnetic Vortices inVery Underdoped yttrium-barium-copper-oxide

Guikema¹

2005

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Since their discovery by Bednorz and Müller (1986), high-temperature cuprate superconductors have been the subject of intense experimental research and theoretical work. Despite this large-scale effort, agreement on the mechanism of high-T c has not been reached. Many theories make their strongest predictions for underdoped superconductors with very low superfluid density n s /m * . For this dissertation I implemented a scanning Hall probe microscope and used it to study magnetic vortices in newly available single crystals of very underdoped YBa 2 Cu 3 O 6+x (Liang et al. 1998. These studies have disproved a promising theory of spin-charge separation, measured the apparent vortex size (an upper bound on the penetration depth λ ab ), and revealed an intriguing phenomenon of "split" vortices.Scanning Hall probe microscopy is a non-invasive and direct method for magnetic field imaging. It is one of the few techniques capable of submicron spatial resolution coupled with sub-Φ 0 (flux quantum) sensitivity, and it operates over a wide temperature range. Chapter 2 introduces the variable temperature scanning microscope and discusses the scanning Hall probe set-up and scanner characterizations. Chapter 3 details my fabrication of submicron GaAs/AlGaAs Hall probes and discusses noise studies for a range of probe sizes, which suggest that sub-100 nm probes could be made without compromising flux sensitivity.The subsequent chapters detail scanning Hall probe (and SQUID) microscopy studies of very underdoped YBa 2 Cu 3 O 6+x crystals with T c ≤ 15 K. Chapter 4 describes two experimental tests for visons, essential excitations of a spin-charge separation theory proposed by Fisher (2000, 2001b). We searched for predicted In regards to the Hall probes, I thank David Kisker (formerly at IBM), and Hadas Shtrikman at Weizmann, for growing the GaAs/AlGaAs 2DEG wafers on which the probes were made. The Marcus group gave me advice on GaAs processes early on. In my attempted measurements of the penetration depth from vortex images, I thank the following people for helpful discussions with us:

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Magnetic microscopy using SQUIDs

Cited by 32 publications

References 16 publications

High-frequency near-field microscopy

High-frequency near-field microscopy

Scanning Squid Microscopy

Scanning Hall Probe Microscopy of Magnetic Vortices inVery Underdoped yttrium-barium-copper-oxide

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