Analysis of the 4-junction SQUID

Suzuki, K.; Okabe, Yoshinobu

doi:10.1109/77.233323

Cited by 8 publications

(9 citation statements)

References 5 publications

(1 reference statement)

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“…For every field value > < , we define the optimal working point as the set of bias and control currents 4# , 41 corresponds to about half a period. However, by utilizing both control currents along a diagonal curve like the dotted white line, a shift of > < M<N of about a full period is achieved.…”

Section: S6 Optimal Working Pointsmentioning

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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Section: S6 Optimal Working Pointsmentioning

confidence: 99%

Electrically Tunable Multiterminal SQUID-on-Tip

et al. 2016

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“…We have numerically verified, for few values of the parameters, that the reduced system of six equations yelds the same results of the originary system, Eqs. (4)(5)(6). This was checked with increasing number of junctions up to N= 20 junctions per branch.…”

Section: The 2n-junction Squid Modelmentioning

confidence: 99%

“…Two linear arrays, each containing N Josephson junctions, closed into a superconductor loop constitute a 2N-junction SQUID (Superconducting QUantum Interference Device), (see Fig.1). Such multijunction structures are of interest in designing high gain SQUIDs [1,2,3,4]. The case with a single junction for each branch (N=1) is the well studied case of a dc-SQUID [5,6,7].…”

Section: Introductionmentioning

confidence: 99%

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Constants of motion in the dynamics of a 2N-junction SQUID

Nappi¹,

Филатрелла²,

Pagano³

1995

Physics Letters A

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We show that a 2N junction SQUID (Superconducting QUantum Interference Device) made of 2N overdamped, shunted, identical junctions may be described as a system having only 6 degrees of freedom for any N ≥ 3. This is achieved by means of the reduction introduced by Watanabe and Strogatz (Physica D, 74, (1994) 197) for series biased arrays. In our case 6 rather than 3 degrees of freedom are necessary to describe the system, due to the requirement of phase quantization along the superconducting loop constituting the device. Generalization to multijunction parallel arrays is straightforward.

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“…Properties of multijunction superconducting quantum interferometer devices ͑SQUIDs͒, involving junctions connected both in series and in parallel, have been the subject of some previous theoretical [1][2][3][4][5][6][7] and experimental 8-10 investigations. Recently new interest was caused on the one hand by the fact that popular step-edge technology used to fabricate a single high-T c dc Josephson junction always leads to a twojunction system, and on the other by expectations of some specific applications of such SQUIDs ͑cf.…”

Section: Introductionmentioning

confidence: 99%

Equilibrium states in multijunction superconducting quantum interferometers

Konopka

Lewandowski

Mikheenko

et al. 1996

Journal of Applied Physics

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Multijunction superconducting quantum interferometers can be created spontaneously by intrinsic junctions in granular high-T c materials, and as a by-product of step-edge technology used to fabricate high-T c thin film dc superconducting quantum interference devices. The properties of such systems are relatively little known. The theory predicts multivalued dependence of critical current I c on applied magnetic flux ⌽ e and the appearance of different stationary ''phase states'' related to different possible relationships between the phases of superconducting order parameter in individual junctions. We report on the measurements performed on a ͑2ϫ2͒ quantum interferometer, comprising a series array of two underdamped all-niobium tunnel junctions in each parallel arm. Experimental results closely follow the theoretical predictions and reveal several instability regions, in which noise generation takes place. These findings can possibly be related to the random telegraph noise observed in high-T c materials.

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Analysis of the 4-junction SQUID

Cited by 8 publications

References 5 publications

Electrically Tunable Multiterminal SQUID-on-Tip

Electrically Tunable Multiterminal SQUID-on-Tip

Constants of motion in the dynamics of a 2N-junction SQUID

Equilibrium states in multijunction superconducting quantum interferometers

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