Myriam Pannetier-Lecoeur

Atomic Energy and Alternative Energies Commission | CEA · Centre d'Etudes de Saclay

Detecting orbital magnetism Graphene’s electronic structure has been predicted to lead to an unusual orbital response to magnetic fields. However, detecting this orbital magnetism is difficult because it is usually masked by the signal stemming from spins. Vallejo Bustamante et al . managed to capture this response by placing two giant magnetoresis...

In the above article [1] , unfortunately, errors were present in Table I , for the correction factors of the 1/4 Wheatstone bridge regarding the thermal noise, the shot noise, and the Hooge parameter entry. The errors have no influence on the experimental results, neither on the other table nor on the discussion and conclusions of the article....

In this manuscript we propose a calculation method where the magneto-resistive elements are modelled as fluctuating resistances to correct the output voltage noise of magnetic tunnel junction (MTJ) from standard electronic circuits. This method is validated on single elements, partial and full Wheatstone bridge circuits, giving rise to a correction...

The performance of magnetoresistive sensors is today mainly limited by their 1/f low-frequency noise. Here, we study this noise component in vortex-based TMR sensors. We compare the noise level in different magnetization configurations of the device, i.e., vortex state or uniform parallel or antiparallel states. We find that the vortex state is at...

In this letter, we present a study of optimized TMR magnetic field sensors as a function of voltage bias. The 1/f low-frequency noise is quantified by the Hooge-like parameter {\alpha} which allows to compare the low-frequency behavior of various TMR sensors. The sensitivity as well as the detectivity of the sensor are characterized in the parallel...

In this manuscript we propose a theoretical model where the magneto-resistive elements are modelled as fluctuating resistances to correct the output voltage noise of tunnel magnetic junction (MTJ) from standard electronic circuits. This model is validated on single elements, partial and full Wheatstone bridge circuits, giving rise to a correction f...

Performance of magnetoresistive sensors is today mainly limited by their 1/f low-frequency noise. Here, we study this noise component in vortex-based TMR sensors. We compare the noise level in different magnetization configurations of the device, i.e vortex state or uniform parallel or antiparallel states. We find that the vortex state is at least...

The electronic properties of graphene have been intensively investigated over the last decade, and signatures of the remarkable features of its linear Dirac spectrum have been displayed using transport and spectroscopy experiments. In contrast, the orbital magnetism of graphene, which is one of the most fundamental signature of the characteristic B...

Neuronal electrical activity is widely studied in vivo, and the ability to measure its magnetic equivalent to obtain an undisturbed signal with both amplitude and direction information leading to neuronal signal mapping would be a promising tool for neuroscience. To provide such a tool, a probe with spin-electronics-based magnetic sensors with orth...

Vertical packaging of multiple giant magnetoresistance (multi-GMR) stacks is a very interesting noise reduction strategy for local magnetic sensor measurements, which has not been reported experimentally so far. Here, we fabricate multi-GMR sensors (up to 12 repetitions) that maintain a good GMR ratio, linearity, and low roughness. From magnetotran...

Vertical packaging of multiple Giant Magnetoresistance (multi-GMR) stacks is a very interesting noise reduction strategy for local magnetic sensor measurements, which has not been reported experimentally so far. Here, we have fabricated multi-GMR sensors (up to 12 repetitions) keeping good GMR ratio, linearity and low roughness. From magnetotranspo...

The 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...

The 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...

This 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...

Neuronal activity generates ionic flows and thereby both magnetic fields and electric potential differences, i.e., voltages. Voltage measurements are widely used but suffer from isolating and smearing properties of tissue between source and sensor, are blind to ionic flow direction, and reflect the difference between two electrodes, complicating in...

Spin electronics has opened new path for improving magnetic detection for medical or neurosciences applications. In this chapter, we will cover main aspects of these developments related to magnetic resonance imaging and magnetophysiology.

All-oxide magnetic tunnel junctions with a semiconducting barrier, formed by the half-metallic ferromagnet La0.7Sr0.3MnO3 and n-type semiconductor SrTi0.8Nb0.2O3, were designed, fabricated, and investigated in terms of their magneto-transport properties as a function of applied bias and temperature. We found that the use of the heavily Nb-doped SrT...

The electrical activity of brain, heart and skeletal muscles generates magnetic fields but these are recordable only macroscopically, such as in magnetoencephalography, which is used to map neuronal activity at the brain scale. At the local scale, magnetic fields recordings are still pending because of the lack of tools that can come in contact wit...

Neuronal activity generates ionic flows and thereby both magnetic fields and electric potential differences, i.e. voltages. Voltage measurements are widely used, but suffer from isolating and smearing properties of tissue between source and sensor, are blind to ionic flow direction, and reflect the difference between two electrodes, complicating in...

Nuclear Magnetic Resonance (NMR) spectroscopy on small volumes, either on microfluidic channels or in vivo configuration, is a present challenge. We report here a high resolution NMR spectroscopy on micron scale performed with Giant Magnetic Resistance-based sensors placed in a static magnetic B0 field of 0.3 T. The sensing volume of the order o...

We present a method to fabricate top-gated field-effect devices in a LaAlO3/SrTiO3 two-dimensional electron gas (2-DEG). Prior to the gate deposition, the realisation of micron size conducting channels in the 2-DEG is achieved by an ion-irradiation with high-energy oxygen ions. After identifying the ion fluence as the key parameter that determines...

To detect magnetic signals coming from the body, in particular those produced by the electrical activity of the heart or of the brain, the development of ultrasensitive sensors is required. In this regard, magnetoresistive sensors, stemming from spin electronics, are very promising devices. For example, tunnel magnetoresistance (TMR) junctions base...

The invention relates to an integrated sensor, including terminals (1, 2) for connection to an electric generator, said terminals being connected to a metal measuring line (4, 5) in which a current proportional to the voltage or current of the generator to be measured flows, and magnetoresistors (31, 32, 33, 34). The metal measuring line includes e...

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...

Ultra-low temperature sensors provide unprecedented performances in X-ray and far infrared astronomy by taking advantage of physical properties of matter close to absolute zero. CESAR is an FP7 funded project started in December 2010, that gathers six European laboratories around the development of high performances cryogenic electronics. The goal...

A very low field magnetic resonance imaging (MRI) setup based on magnetoresistive-superconducting mixed sensors is presented. A flux transformer is used to achieve coupling between the sample to image and the mixed sensor. The novel detector was implemented in a spin echo MRI experiment, exposing the mixed sensor to RF pulses without use of any RF...

The method for cancellation of low frequency noise in a magneto-resistive mixed sensor (1) comprising at least a superconducting loop with at least one constriction and at least one magneto-resistive element (6) comprises a set of measuring steps with at least one measuring step being conducted with the normal running of the mixed sensor and at lea...

A device comprises a mixed sensor design with at least one superconducting loop (1) containing at least one constriction (3) and a magneto-resistive element (2) located next to the constriction (3). The device contains at least one heating element (5) that allows switching at sufficiently high frequency of at least one part of the superconducting l...

This study presents NMR signal detection by means of a superconducting channel consisting of a Nb surface detection coil inductively coupled to a YBCO mixed sensor. The NMR system operates at a low-field (8.9 mT) in a magnetically shielded room suitable for magnetoencephalographic (MEG) recordings. The main field is generated by a compact solenoid...

Giant Magnetoresistances (GMR) and Tunnel Magnetoresistances (TMR) take an increasing part in many applications like current sensing, magnetometry or position sensing, thanks to their high magnetoresistance at room temperature, which leads to a large output signal variation. But the real performances of such sensors can only be estimated with respe...

Mixed sensors are very sensitive magnetic field detectors based on the combination of a superconducting loop and magnetoresistive elements, which have already demonstrated their capability to record biomagnetic signals. However, in order to employ these devices in new apparatus, it would be suitable to arrange them in arrays. Here we report the fir...

We have studied the antiferromagnetic coupling at the interface of the La0.7Sr0.3MnO3/SrRuO3 bilayer as function of temperature. We measured the La0.7Sr0.3MnO3 magnetization reversal while the SrRuO3 magnetization is blocked due to a field cooled procedure and because of its high coercive field. Even if in this system, the La0.7Sr0.3MnO3 magnetizat...

We have studied the magnetic hysteresis cycle of La_{0.67}Sr_{0.33}MnO_{3}/SrRuO_{3} antiferromagnetically coupled bilayers, by magnetometry and polarized neutron reflectometry. A positive exchange bias as well as an unusual asymmetry are observed on the magnetic reversal process of the La_{0.67}Sr_{0.33}MnO_{3} layer. Through an extended Stoner-Wo...

In this short chapter, we present an alternative approach for biomagnetic signals detection using spin electronics based magnetic sensors. The principle of these sensors is first given followed by examples of their use for magnetocardiography and low field MRI. © 2014 Springer-Verlag Berlin Heidelberg. All rights are reserved.

Magnetic tunnel junctions based on manganites can exhibit a high tunneling magnetoresistance ratio due to the almost full spin polarization at the Fermi level. However, the performances of magnetic tunnel junction devices are also strongly linked to their noise characteristics. Here, we present a low frequency noise study on fully epitaxial La0.7Sr...

We have previously proposed a model for the flux creep regime of the vortices in superconducting thin film microbridges in which a bias current flows. In the first part of the paper this model is summarized and we show how physical quantities which are relevant to estimate the importance of vortex pinning in the samples can be determined. Then, the...

CEA, a prominent player in research, development and innovation has developed extensive expertise in a number of topics which are now central within the global security research issues. As an example, CEA is developing research of new technologies for the detection of explosives. This article gives an overview of the main activities regarding to th...

Since the fundamental discovery of the giant magnetoresistance many spintronic devices have been developed and implemented in our daily life (e.g. information storage and automotive industry). Lately, advances in the sensors technology (higher sensitivity, smaller size) have potentiated other applications, namely in the biological area, leading to...

Spin electronics sensors can be used as magnetic field sensors in various applications such as current sensing, non-destructive testing or compasses. While metallic layers are used for most of the room temperature applications, oxide materials exhibit very good performances for low temperature applications. Here we present the principle of an all-o...

We present an integrated voltage sensor dedicated to fuel cells monitoring. This sensor is based on Giant Magneto Resistances (GMR) as sensitive elements coupled to a micron size integrated metallic line which creates a field on the GMR elements when a current flows in it. Complete module containing eight channels with the associated electronics ha...

We have developed La0.7Sr0.3MnO3 (LSMO) based spin valve tunnel junctions where the hard layer is composed of Ru doped La0.7Sr0.3MnO3 (LSMRO). These perovskite oxide layers have been grown on SrTiO3 by pulsed laser deposition. X ray diffraction, transmission electron microscopy and atomic force microscope measurements show the crystalline quality o...

Low-field magnetic resonance imaging (MRI) requires very sensitive magnetometers for detection of weak magnetic signals in femtoTesla range. Magnetoresistive mixed sensors could be used as the sensitive magnetometers [1]. These sensors are the combination of a Giant Magnetoresistive (GMR) field sensor and a superconducting loop used as a flux-to-fi...

SrTiO3 (STO) is a band insulator with a perovskite crystallographic structure, widely used as substrate for the deposition of other perovskite materials, for instance manganites or cuprates. STO surface becomes conductive under Ar+ ion irradiation, exhibiting similar properties to STO/LaAlO3 interface or bulk reduced STO. We report the transport an...

We have developed a sensor based on the Giant Magneto-Resistive (GMR) effect, associated to a superconducting flux-to-field transformer, which allows femtotesla field detection in a wide range of frequencies [1]. Such sensors are good candidates for measurements of biomagnetic signals generated by the brain or the heart. Here we present Magneto-Car...

Biomagnetic signals, mostly due to the electrical activity in the body, are very weak and they can only be detected by the most sensitive magnetometers, such as Superconducting Quantum Interference Devices (SQUIDs). We report here biomagnetic recordings with hybrid sensors based on Giant MagnetoResistance (GMR). We recorded magnetic signatures of t...

We report the transport and noise properties as function of temperature and electric field of Ar+ irradiated SrTiO3 exhibiting at its surface a high-mobility electron gas. This system exhibits metallic properties with low-charge densities allowing mobility measurements. The low-frequency /f noise presents a linear dependence with the mobility. This...

When coupled to a giant magnetoresistive (GMR) sensor, a superconducting loop containing a constriction can be a very sensitive magnetometer. It has thermal noise levels of few fT/sqrt(Hz), comparable to low-Tc SQUID noise, with a flat frequency response. These mixed sensors are good candidates for detection of weak biomagnetic signals, like a card...

Low-frequency noise has been measured in magnetic tunnel junctions with MgO barriers and magnetoresistance values up to 235%. We present here the noise for different degrees of crystallization and CoFeB/MgO interface quality depending on the annealing temperature. For optimized annealing temperature, an extremely low 1/f noise, compared to magnetic...

In order to measure extremely weak magnetic fields, such as those produced by the neuronal activity during cognitive tasks in the brain, we have proposed and realized a femtotesla (10-15T) sensor based on the association of spin electronics and superconductivity which offers an alternative in thin film technology and at 77K to the most sensitive de...

Recently developed magnetoresistive hybrid sensors can detect magnetic signals in the femtotesla range. This sensor is a combination of a Giant Magnetoresistive (GMR) field sensor and flux-to-field superconducting transformer [1]. Hybrid sensors are the good candidates for Low-Field Magnetic Resonance Imaging (LF-MRI) and neural signal detection. T...

In order to bring an alternative solution to the high-performance but complex low-Tc SQUID microscope for small-scale rock magnetic investigations, we propose a room-temperature and rugged scanning magnetic microscope prototype. This new device uses a Giant Magneto Resistance (GMR) sensor that is sensitive to the in-plane components of the magnetic...

An integrated device including microfluidic channels and incorporated magnetoresistive spin valve sensors has been developed and used to detect single magnetic bead motion at cm/s velocities. The sensitivity of the system is high enough to determine the magnetic orientation, the flowing height and the speed of each particle for velocities between 1...

We have developed a new scanning magnetic microscope to image with micrometric resolution magnetic fields originating from room temperature polished samples. This microscope is based on a giant magnetoresistance (GMR) sensor working at room temperature. These magnetic sensors are sensitive to the in-plane components of the magnetic field. The size...

Ultra-sensitive magnetometry addresses the detection of extremely small magnetic signals, typically in the femtotesla range, and is required for magnetic brain signal acquisition (Magnetoencephalography) and Low-Field Magnetic Resonance Imaging (LF-MRI). Superconducting Quantum Interference Devices (SQUIDs) have been since forty years the most appr...

This work describes an integrated device comprising microfluidic channels and incorporated spin-valve sensors sensitive enough to count, determine the magnetic orientation, flowing height, and speed of single micron-sized magnetic beads moving with velocities of 8–35 mm/s. Sensor signals of 3–100 μVp-p correspond to bead moments at different direct...

Nuclear Quadrupolar Resonance of nitrogen allows selective detection of solid explosives containing Nitrogen. That technique has the advantage to be highly selective but its sensitivity is poor, in particular for some products presenting long relaxation time like Tri-Nitro-Toluene (TNT). The limitation is given by the noise of the detecting system,...

Flux transformers are currently used for signal detection with high sensitivity magnetometers like SQUIDS , as an alternative to direct coupling between the magnetometer and the sample. To avoid extra noise, most of them are made of superconducting material, namely low critical temperature (Tc) wires and high Tc thin films. We build flux transforme...

We have developed a very sensitive field sensor to detect magnetic signals in the femtotesla range. This mixed sensor is based on the association of a superconducting flux-to-field transformer with a magnetoresistive field sensor. The bandwidth of a GMR being wide and only limited in the GHz regime, where the ferromagnetic resonance of the free lay...

Low frequency noise and small output voltage are the strongest limitations to the use of magnetic tunnel junctions (MTJs) for magnetic sensor applications, replacing giant magnetoresistance (GMR) and anisotropic magnetoresistance sensors. In this paper, we explore the possibility of using arrays with a large number of MTJs connected in parallel/ser...

We have designed flux transformers made of commercial BiSCCO tapes closed by soldering with normal metal. The magnetic field transfer function of the flux transformer was calculated as a function of the resistance of the soldered contacts. The performances of different kinds of wires were investigated for signal delocalization and gradiometry. We a...

The feasibility to develop mini- and micro-magnetic electro-mechanical systems (MEMS) has been evaluated by prototyping of a single-phase stepper motor. The main targeted application of such device is the watch industry needing micro-motors in huge quantities at low cost. The motor part that required the greatest efforts has been the magnet, which...

Magnetoresistive materials are widely used for read-heads and are very good candidates for sensors due to their sensitivity. A large number of applications, at present covered by Hall sensors, can be targeted but they require having stable, reproducible, hysteresis-free and high signal-to-noise devices. This can be addressed by optimizing the mater...

A device for non destructive evaluation of defects in a metallic object (2) by eddy currents, comprises a field emitter (3) for emitting an alternating electromagnetic field at a first frequency fi in the neighbourhood of the metallic object (2), and a magnetoresistive sensor (1) for detecting a response signal constituted by a return electromagnet...

Low frequency noise has been measured in magnetic tunnel junctions with MgO barriers and magnetoresistance values up to 235%. We investigated the noise for different degrees of crystallization and CoFeB/MgO interface quality depending on the annealing temperature. We report an extremely low 1/f noise, compared to magnetic junctions with Al2O3 barri...

When coupled to a Giant Magneto-Resistive (GMR) sensor, a superconducting loop containing a constriction can be a very sensitive device for magnetic field detection . The bandwidth of a GMR sensor is wide with only a limitation in the GHz regime mainly due to the ferromagnetic resonances of the free layer. We have studied the radiofrequency respons...

Low frequency noise has been measured in magnetic tunnel junctions with MgO barriers and magnetoresistance values up to 235%. The authors investigated the noise for different degrees of crystallization and CoFeB/MgO interface quality depending on the annealing temperature. The authors report an extremely low 1/f noise, compared to magnetic junction...

Neutron reflectometry with spin analysis has allowed us to perform selective hysteresis loops of each magnetic layer in GMR spin valves. The intensities now available on reflectometers and the advances of modelling give the possibility to perform a very precise analysis of the magnetic configuration even in complex systems with five different magne...