Spatial Resolution Assessment of Nano-SQUIDs Made by Focused Ion Beam

Líu, Hao; Macfarlane, J.C.; Gallop, John; Romans, E.J.; Cox, D. C.; Hutson, David; Chen, Jie

doi:10.1109/tasc.2007.898068

Cited by 13 publications

(14 citation statements)

References 5 publications

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“…19 For a circular loop, such increasing can be approximately evaluated as A eff = A g ͕͓1+⌳͑T͒ / a͔͖ 2 , where ⌳͑T͒ = 2 ͑T͒ / d is the two-dimensional Pearl screening length, ͑T͒ is the London penetration depth at the temperature T, d is the superconducting film thickness, and A g is the geometrical area of the SQUID loop. With typical values of loop radius and film thickness employed in nano-SQUID fabrication, the correction factor, in general, cannot be neglected.…”

Section: Methods and Resultsmentioning

confidence: 99%

Performance of nano superconducting quantum interference devices for small spin cluster detection

Granata

Vettoliere

Walke

et al. 2009

Journal of Applied Physics

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In the present paper, performance of nano-superconducting-quantum-interference devices (SQUIDs) has been investigated in view of their employment in the detection of small spin populations. The analysis has been focused on nano-SQUID sensors having a square loop with a side length of 200 nm. We calculate the spin sensitivity and the magnetic response relative to the single Bohr magneton (single spin), as a function of its position within the SQUID hole. The results show that the SQUID response depends strongly on the spin position; the ratio between the spin sensitivity evaluated in the center of the loop and the minimum one is as high as a factor of 3 for a spin at a reasonable distance z′ of 10 nm from the SQUID plane. Furthermore, the magnetic flux due to several hundred of spins has been evaluated by considering different random spin distributions within the SQUID hole. Due to the both nonuniform SQUID response and the random distribution process, the results show a statistical uncertainty which has been evaluated as a function of the spin number. The estimated informations are very useful to optimize the sensor performance in view of the most nanomagnetism applications.

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Section: Methods and Resultsmentioning

confidence: 99%

Performance of nano superconducting quantum interference devices for small spin cluster detection

Granata

Vettoliere

Walke

et al. 2009

Journal of Applied Physics

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“…Moreover, the filamentary model does not consider flux focusing due to finite width of the superconducting tracks [110,145]. For a circular loop, such increasing can be approximately evaluated as A eff =Α g [(1+Λ(T)/a)] 2 where Λ(T)=λ 2 (T)/d is the two-dimensional effective penetration depths [146], λ(T) is the London penetration depth at the temperature T, d is the superconducting film thickness and A g is the geometrical area of the SQUID loop. With typical values of loop radius and film thickness employed in nano-SQUID fabrication, the correction factor may not be negligible.…”

Section: Flux Coupling and Spin Sensitivity Computationmentioning

confidence: 99%

Nano Superconducting Quantum Interference device: A powerful tool for nanoscale investigations

2016

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The magnetic sensing at nanoscale level is a promising and interesting research topic of nanoscience. Indeed, magnetic imaging is a powerful tool for probing biological, chemical and physical systems. The study of small spin cluster, like magnetic molecules and nanoparticles, single electron, cold atom clouds, is one of the most stimulating challenges of applied and basic research of the next years. In particular, the magnetic nanoparticle investigation plays a fundamental role for the modern material science and its relative technological applications like ferrofluids, magnetic refrigeration and biomedical applications, including drug delivery, hyper-thermia cancer treatment and magnetic resonance imaging contrast-agent. Actually, one of the most ambitious goals of the high sensitivity magnetometry is the detection of elementary magnetic moment or spin. In this framework, several efforts have been devoted to the development of a high sensitivity magnetic nanosensor pushing sensing capability to the individual spin level. Among the different magnetic sensors, Superconducting QUantum Interference Devices (SQUIDs) exhibit an ultra high sensitivity and are widely employed in numerous applications. Basically, a SQUID consists of a superconducting ring (sensitive area) interrupted by two Josephson junctions. In the recent years, it has been proved that the magnetic response of nano-objects can be effectively measured by using a SQUID with a very small sensitive area (nanoSQUID). In fact, the sensor noise, expressed in terms of the elementary magnetic moment (spin or Bohr magneton), is linearly dependent on the SQUID loop side length. For this reason, SQUIDs have been progressively miniaturized in order to improve the sensitivity up to few spin per unit of bandwidth. With respect to other techniques, nanoSQUIDs offer the advantage of direct measurement of magnetization changes in small spin systems. In this

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“…The calculated value of the M obtained integrating the magnetic field produced by the coil over the geometrical area of the SQUID is about half the value of the experimental one indicating an effective area greater than the geometrical one. Probably, it is due to the Pearl penetration length which increases the flux capture area [11]. In fact for a circular loop (radius a) consisting of a thin superconductor film (thickness d) the effective area is: [11] where is the two-dimensional Pearls screening length and is the London penetration depth.…”

Section: Measurementsmentioning

confidence: 99%

“…Probably, it is due to the Pearl penetration length which increases the flux capture area [11]. In fact for a circular loop (radius a) consisting of a thin superconductor film (thickness d) the effective area is: [11] where is the two-dimensional Pearls screening length and is the London penetration depth. With typical values of loop radius and film thickness employed in nano-SQUIDs fabrication, the correction factor cannot be neglected.…”

Section: Measurementsmentioning

confidence: 99%

Performance of High-Sensitivity Nano-SQUIDs Based on Niobium Dayem Bridges

Vettoliere

Granata

Esposito

et al. 2009

IEEE Trans. Appl. Supercond.

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Measurements and noise performances of integrated nano superconducting quantum interference devices (nano-SQUIDs) are presented. The nano-sensors are based on nanometric niobium constrictions (Dayem bridges) inserted in a square loop having a side length of 200 nm. Integrated micrometric niobium coils located close to the sensor allow both an easy tuning/calibration and the optimization of the working point. Improved measurements of voltage-flux characteristic, flux to voltage transfer factor and noise performances are reported. In small signal mode, the sensors have shown a magnetic flux noise spectral density of 1.5 8 0 Hz 1 2 . Furthermore, preliminary measurements concerning the critical current vs. temperature dependence and the switching probability of the critical current are shown. Index Terms-Dayem bridge, magnetic sensor, nano-SQUID.

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Spatial Resolution Assessment of Nano-SQUIDs Made by Focused Ion Beam

Cited by 13 publications

References 5 publications

Performance of nano superconducting quantum interference devices for small spin cluster detection

Performance of nano superconducting quantum interference devices for small spin cluster detection

Nano Superconducting Quantum Interference device: A powerful tool for nanoscale investigations

Performance of High-Sensitivity Nano-SQUIDs Based on Niobium Dayem Bridges

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