Microwave-Assisted Magnetization Reversal in Individual Isolated Clusters of Cobalt

Raufast, Cécile; Tamion, Alexandre; Bernstein, E.; Dupuis, V.; Fournier, Thierry; Crozes, T.; Bonet, Edgar; Wernsdorfer, Wolfgang

doi:10.1109/tmag.2008.2002022

Cited by 10 publications

(5 citation statements)

References 8 publications

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“…In this paper, we study the effects of microwave fields on MJJ critical current levels in attempt to find an alternative addressing approach which would minimize the memory cell dimensions. The RF-assisted magnetization switching is a rather well known phenomenon for a wide range of systems such as magnetic clusters, single-domain magnetic particles and magnetic tunnel junctions [19][20][21][22][23][24][25][26][27] , but it has never been investigated on MJJs, although spin wave resonances have been observed in conventional ferromagnetic Josephson junctions 28 . Here we show how this effect of remagnetization boost by RF fields can be used to improve discernibility of two logical states of a superconducting memory element based on Pd 0.99 Fe 0.01 magnetic barrier.…”

Section: Introductionmentioning

confidence: 99%

RF assisted switching in magnetic Josephson junctions

Caruso

Massarotti

Bolginov

et al. 2018

Journal of Applied Physics

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We test the effect of an external RF field on the switching processes of magnetic Josephson junctions (MJJs) suitable for the realization of fast, scalable cryogenic memories compatible with Single Flux Quantum logic. We show that the combined application of microwaves and magnetic field pulses can improve the performances of the device, increasing the separation between the critical current levels corresponding to logical '0' and '1'. The enhancement of the current level separation can be as high as 80% using an optimal set of parameters. We demonstrate that external RF fields can be used as an additional tool to manipulate the memory states, and we expect that this approach may lead to the development of new methods of selecting MJJs and manipulating their states in memory arrays for various applications.

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Section: Introductionmentioning

confidence: 99%

RF assisted switching in magnetic Josephson junctions

Caruso

Massarotti

Bolginov

et al. 2018

Journal of Applied Physics

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“…22) or Nb are suitable candidates); (4) ultralow dissipation (∼1...100 fW), which makes it ideal for nanoscale applications; (5) ease of implementation in a series or parallel array (depending on the biasing mode) for enhanced output; and (6) ease of integration with superconducting refrigerators 23 to actively tune the device working temperature. Finally, as far as specific applications 24 are concerned, measurements of small magnetic systems 25 (for instance, the magnetic flux induced by atomic spins as well as singlemolecule nanomagnets), single-photon detection 26 , scanning microscopy as well as quantum metrology 27 and nanoelectromechanical measurements 28 with SQUIPT devices could be predicted. Our approach opens the way to magnetic-field detection based on 'hybrid' interferometers that take advantage of the flexibility intrinsic to proximity metals.…”

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confidence: 99%

Superconducting quantum interference proximity transistor

et al. 2010

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When a superconductor is placed close to a non-superconducting metal, it can induce superconducting correlations in the metal [1][2][3][4][5][6][7][8][9][10] , known as the 'proximity effect' 11. Such behaviour modifies the density of states (DOS) in the normal metal [12][13][14][15] and opens a minigap 12,13,16 with an amplitude that can be controlled by changing the phase of the superconducting order parameter 12,15 . Here, we exploit such behaviour to realize a new type of interferometer, the superconducting quantum interference proximity transistor (SQUIPT), for which the operation relies on the modulation with the magnetic field of the DOS of a proximized metal embedded in a superconducting loop. Even without optimizing its design, this device shows extremely low flux noise, down to ∼10 −5 Φ 0 HzWb is the flux quantum) and dissipation several orders of magnitude smaller than in conventional superconducting interferometers [17][18][19] . With optimization, the SQUIPT could significantly increase the sensitivity with which small magnetic moments are detected.One typical SQUIPT fabricated with electron-beam lithography is shown in Fig. 1a. It consists of an aluminium (Al) superconducting loop interrupted by a copper (Cu) normal-metal wire in good electric contact with it. Furthermore, two Al electrodes are tunnel-coupled to the normal region to enable the device operation. A detailed view of the sample core (see Fig. 1b) shows the Cu region of length L 1.5 µm and width 240 nm coupled to the tunnel probes and the superconducting loop. The SQUIPTs were implemented into two different designs (see Fig. 1c), namely, the A-type configuration, where the loop extends into an extra third lead, and the B-type configuration, which contains only two tunnel probes. The ring geometry enables us to change the phase difference across the normal-metal/superconductor boundaries through the application of an external magnetic field, which gives rise to a total flux Φ through the loop area. This modifies the DOS in the normal metal, and hence the transport through the tunnel junctions.Insight into the interferometric nature of the SQUIPT can be gained by first analysing the theoretical prediction of its behaviour. Figure 2a shows the simplest implementation of the device in the A-type configuration, that is, that with just one junction tunnelcoupled to the normal metal. For simplicity, we suppose the tunnel probe (with resistance R T ) to be placed in the middle of the wire, and to feed a constant electric current I through the circuit while the voltage drop V is recorded as a function of Φ. In the limit that the kinetic inductance of the superconducting loop is negligible, the magnetic flux fixes a phase difference φ = 2πΦ/Φ 0 across the normal metal, where Φ 0 = πh/e is the flux quantum,h is the reduced Planck's constant and e is the electron charge. Figure 2b shows the low-temperature quasiparticle current-voltage (I -V ) characteristic of the SQUIPT calculated at a few selected values of Φ. The calculations were carried out f...

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“…Since that time, various approaches have been attempted such as using a quartz fibre torsion balance, optical methods, electron holography, vibrating reed magnetometry, Lorentz microscopy and magnetic force microscopy. Very recently, Raufast et al [20] have used microSQUIDs to detect the magnetic reversal of 3 nm cobalt particles (approximately 1000 spins) embedded in a germanium matrix. The first challenge is the placement of a single nanoparticle close to the nanoSQUID while achieving sufficient magnetic coupling between the particle and the device.…”

Section: Measurement Of Small Magnetic Systemsmentioning

confidence: 99%