Field-effect control of superconductivity and Rashba spin-orbit coupling in top-gated LaAlO3/SrTiO3 devices

The recent development in the fabrication of artificial oxide heterostructures opens new avenues in the field of quantum materials by enabling the manipulation of the charge, spin and orbital degrees of freedom. In this context, the discovery of two-dimensional electron gases (2-DEGs) at LAlO3/SrTiO3 interfaces, which exhibit both superconductivity and strong Rashba spin-orbit coupling (SOC), represents a major breakthrough. Here, we report on the realisation of a field-effect LaAlO3/SrTiO3 device, whose physical properties, including superconductivity and SOC, can be tuned over a wide range by a top-gate voltage. We derive a phase diagram, which emphasises a field-effect-induced superconductor-to-insulator quantum phase transition. Magneto-transport measurements indicate that the Rashba coupling constant increases linearly with electrostatic doping. Our results pave the way for the realisation of mesoscopic devices, where these two properties can be manipulated on a local scale by means of top-gates

Enhancing the sensitivity of magnetic sensors by 3D metamaterial shells

Magnetic sensors are key elements in our interconnected smart society. Their sensitivity becomes essential for many applications in fields such as biomedicine, computer memories, geophysics, or space exploration. Here we present a universal way of increasing the sensitivity of magnetic sensors by surrounding them with a spherical metamaterial shell with specially designed anisotropic magnetic properties. We analytically demonstrate that the magnetic field in the sensing area is enhanced by our metamaterial shell by a known factor that depends on the shell radii ratio. When the applied field is non-uniform, as for dipolar magnetic field sources, field gradient is increased as well. A proof-of-concept experimental realization confirms the theoretical predictions. The metamaterial shell is also shown to concentrate time-dependent magnetic fields upto frequencies of 100 kHz

Optimised GMR sensors for low and high frequencies applications

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RF Response of Superconducting-GMR Mixed Sensors, Application to NQR

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Determination of vortex motion characteristics, effective thickness and dynamic resistance in very thin YBaCuO bilayer structures

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3D magnetic imaging with GMR sensors

International audienceThis paper reports on the development of spin electronics based probes for 3D magnetic imaging. We have demonstrated the feasibility of using four orientations of magnetoresistive sensors (GMR) for the reconstruction of three dimensional components of magnetic field at the same measurement point. The use of different GMR sensor structures makes it possible to adapt the sensitivity and field range to the signal to detect for a specific application. Their characteristics and field reconstruction steps are also shown. Different examples of magnetic imaging are presented

Spin Electronics-Based Magnetic Sensors for Biomagnetic Measurements

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Magnetocardiography with sensors based on giant magnetoresistance

International audienceBiomagnetic signals, mostly due to the electrical activity in the body, are very weak and they canonly be detected by the most sensitive magnetometers, such as Superconducting QuantumInterference Devices SQUIDs. We report here biomagnetic recordings with hybrid sensors basedon Giant MagnetoResistance GMR.We recorded magnetic signatures of the electric activity of thehuman heart magnetocardiography in healthy volunteers. The P-wave and QRS complex, knownfrom the corresponding electric recordings, are clearly visible in the recordings after an averagingtime of about 1 min. Multiple recordings at different locations over the chest yielded a dipolarmagnetic field map and allowed localizing the underlying current sources. The sensitivity of theGMR-based sensors is now approaching that of SQUIDs and paves way for spin electronics devicesfor functional imaging of the body

Optimizing magnetoresistive sensor signal-to-noise via pinning field tuning

International audienceThe presence of magnetic noise in magnetoresistive-based magnetic sensors degrades their detection limit at low frequencies. In this paper, different ways of stabilizing the magnetic sensing layer to suppress magnetic noise are investigated by applying a pinning field, either by an external field, internally in the stack, or by shape anisotropy. We show that these three methods are equivalent, could be combined, and that there is a competition between noise suppression and sensitivity reduction, which results in an optimum total pinning field for which the detection limit of the sensor is improved up to a factor of 10.We acknowledge the following organisms for funding: The CEA for the internal funded projects MIMOSA and CALM and the Ph.D. Grant “Phare Amont-Aval,” the Swiss National Science Foundation for a mobility fellowship (Nos. 165238 and 177732) to A. Doll, ANR funding through Grant Nos. ANR-17-CE19-0021-01 (NeuroTMR) and ANR-18-CE42-0001 (CARAMEL). This work was supported by the EMPIR JRP 15SIB06 NanoMag through EU and EMPIR participating countries within EURAMET