High resolution magnetic imaging: MicroSQUID Force Microscopy

Hasselbach, K.; Ladam, Cecile; Dolocan, Voicu; Hykel, Danny; Crozes, T.; Schuster, K.; Mailly, D.

doi:10.1088/1742-6596/97/1/012330

Cited by 13 publications

(17 citation statements)

References 24 publications

(28 reference statements)

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“…Scanning micro-and nanoscale SQUIDs are of particular interest for magnetic imaging due to their high sensitivity and large bandwidth 15,19 . The two main technological approaches to the fabrication of scanning SQUIDs are based on planar lithographic methods 21,26,[33][34][35][36] and on self-aligned SQUIDon-tip (SOT) deposition 22,24,37 .In the planar SQUID architecture, spatial resolution is limited but pickup and modulation coils can be integrated to allow operation of the SQUID at optimal flux bias conditions using a fluxlocked loop (FLL) feedback mechanism 15,18,19,21,33,38,39 . Because the magnetic field of the sample is not coupled to the SQUID loop directly, but rather through a pickup coil, integration of a modulation coil or an integrated current-carrying element 15,19,21,33,38,39 allows the total flux in the SQUID loop to be maintained at its optimal bias while the magnetic field of the sample is varied independently.…”

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confidence: 99%

Electrically Tunable Multiterminal SQUID-on-Tip

et al. 2016

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We present a new nanoscale superconducting quantum interference device (SQUID) whose interference pattern can be shifted electrically in-situ. The device consists of a nanoscale fourterminal/four-junction SQUID fabricated at the apex of a sharp pipette using a self-aligned threestep deposition of Pb. In contrast to conventional two-terminal/two-junction SQUIDs that display optimal sensitivity when flux biased to about a quarter of the flux quantum, the additional terminals and junctions allow optimal sensitivity at arbitrary applied flux, thus eliminating the magnetic field "blind spots". We demonstrate spin sensitivity of 5 to 8 µ B /Hz 1/2 over a continuous field range of 0 to 0.5 T, with promising applications for nanoscale scanning magnetic imaging.KEYWORDS: superconducting quantum interference device, SQUID on tip, nanoscale magnetic imaging, current-phase relations 2 In recent years, there has been a growing effort to develop and apply nanoscale magnetic imaging tools in order to address the rapidly evolving fields of nanomagnetism and spintronics.These include magnetic force microscopy (MFM) 1,2 , magnetic resonance force microscopy (MRFM) [3][4][5] , nitrogen vacancy (NV) centers sensors [6][7][8][9] , scanning Hall probe microscopy (SHPM) 10-12 , x-ray magnetic microscopy (XRM) 13 , and micro-or nano-superconducting quantum interference device (SQUID) [14][15][16][17][18][19][20] based scanning microscopy (SSM) [21][22][23][24][25][26][27][28][29][30][31][32] . Scanning micro-and nanoscale SQUIDs are of particular interest for magnetic imaging due to their high sensitivity and large bandwidth 15,19 . The two main technological approaches to the fabrication of scanning SQUIDs are based on planar lithographic methods 21,26,[33][34][35][36] and on self-aligned SQUIDon-tip (SOT) deposition 22,24,37 .In the planar SQUID architecture, spatial resolution is limited but pickup and modulation coils can be integrated to allow operation of the SQUID at optimal flux bias conditions using a fluxlocked loop (FLL) feedback mechanism 15,18,19,21,33,38,39 . Because the magnetic field of the sample is not coupled to the SQUID loop directly, but rather through a pickup coil, integration of a modulation coil or an integrated current-carrying element 15,19,21,33,38,39 allows the total flux in the SQUID loop to be maintained at its optimal bias while the magnetic field of the sample is varied independently.SOTs, in contrast, have better spatial resolution due to their small size and close proximity to the sample, attain higher spin sensitivity, and can operate at high magnetic fields 24 . The nanoscale proximity of the SOT to the sample surface, which is its key advantage, dictates however that the flux in the SQUID loop is directly coupled to the local field of the sample and therefore cannot be modified independently. As a result, the FLL concept cannot be implemented in direct nanoscale magnetic imaging. This poses a significant drawback, since the high sensitivity of the SOT is achieved only at specific field va...

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confidence: 99%

Electrically Tunable Multiterminal SQUID-on-Tip

et al. 2016

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“…Micrometer-size SQUIDs (see, e.g. [2,21,22]) can be mechanically cut out and formed using a diamond saw and 4000 grit sandpaper with a precision down to about ∼10 µm, which is limited by the grain size in the sandpaper of ∼6 µm and by the brittleness of the Si: see [21] and figure 5. The SiO 2 layer on the surface of the Si substrate increases the roughness of the mechanically-ground corner of the cantilever considerably.…”

Section: Preparation Of Nanosquid Cantilever Chipsmentioning

confidence: 99%

Bulk nanomachining of cantilevers with Nb nanoSQUIDs based on nanobridge Josephson junctions

Faley¹,

Bikulov²,

Vincent³

et al. 2021

Supercond. Sci. Technol.

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Nanometer-scale superconducting quantum interference devices (nanoSQUIDs) were fabricated within a distance of 1 µm from the corners of 2 × 2 × 0.05 mm Si cantilevers that are intended for use in a scanning nanoSQUID microscope. The nanoSQUIDs contained Josephson junctions (JJs) in the form of Nb-based nanobridges, which had widths down to 10 nm and were patterned using hydrogen silsesquioxane negative resist. Numerical simulations of the superconducting current and the spatial distribution of the order parameter in the nanobridge JJs and the nanoSQUID, as well as the current–phase relationship in the nanobridge JJs, were performed according to Ginzburg–Landau equations on one-dimensional and two-dimensional grids. Bulk micromachining of the Si cantilever was performed using reactive ion etching with SF6 gas through masks of nLOF 2020 photoresist from the front side and a quartz shadow mask from the back side of the substrate. An etch rate of 6 µmmin−1 for Si was achieved for a power of 300 W of the inductively coupled SF6 plasma. The nanoSQUIDs exhibited non-hysteretic current–voltage characteristics on the cantilever. The estimated spin sensitivity of 48 µ B (√Hz)−1 is sufficient for use of such a nanoSQUID as a magnetic field sensor for studying nanoscale objects, with a projected total distance to the object of below 100 nm.

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“…The superconducting ring has attracted considerable attention in the context of both fundamental superconductor research and application, because of its geometryrelated effects, such as fluxoid quantization and quantum interference. [1][2][3][4][5] The magnetic flux, or more precisely, magnetic fluxoid, through an ordinary superconducting ring is quantized in units of h/2e, where h is Planck's constant and e is the electron charge. 1 In superconducting devices and applications, a superconducting ring with or without Josephson junctions has acted as a key element.…”

Section: Introductionmentioning

confidence: 99%

Precise determination of magnetic moment of a fluxoid quantum in a superconducting microring

Choi¹,

Kim²,

Lee³

et al. 2017

Phys. Rev. B

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Using dynamic cantilever magnetometry and experimentally determining the cantilevers vibrational mode shape, we precisely measured the magnetic moment of a lithographically defined micronsized superconducting Nb ring, a key element for the previously proposed subpiconewton force standard. The magnetic moments due to individual magnetic fluxoids and a diamagnetic response were independently determined at T = 4.3 K, with a subfemtoampere-square-meter resolution. The results show good agreement with the theoretical estimation yielded by the Brandt and Clem model within the spring constant determination accuracy. arXiv:1701.07598v1 [cond-mat.mes-hall]

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High resolution magnetic imaging: MicroSQUID Force Microscopy

Cited by 13 publications

References 24 publications

Electrically Tunable Multiterminal SQUID-on-Tip

Electrically Tunable Multiterminal SQUID-on-Tip

Bulk nanomachining of cantilevers with Nb nanoSQUIDs based on nanobridge Josephson junctions

Precise determination of magnetic moment of a fluxoid quantum in a superconducting microring

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