Jean Chazelas

Bio: Jean Chazelas is an academic researcher from Thales Group. The author has contributed to research in topics: Optical fiber & Microwave. The author has an hindex of 19, co-authored 92 publications receiving 8504 citations.

Giant magnetoresistance of (001)Fe/(001)Cr magnetic superlattices.

Abstract: We have studied the magnetoresistance of (001)Fe/(001)Cr superlattices prepared by molecularbeam epitaxy. A huge magnetoresistance is found in superlattices with thin Cr layers: For example, with ${t}_{\mathrm{Cr}}=9$ \AA{}, at $T=4.2$ K, the resistivity is lowered by almost a factor of 2 in a magnetic field of 2 T. We ascribe this giant magnetoresistance to spin-dependent transmission of the conduction electrons between Fe layers through Cr layers.

Process and system for determining the position and orientation of a vehicle, and applications

Abstract: The present invention relates to a process and a system for determining the position and orientation of a mobile, and to applications thereof. In order to ascertain both the position and orientation of a mobile, the invention proposes an interrogation/response process whose particular feature is to supply, to a given interrogation, two responses which are distinguished on the one hand, by different modulating frequencies and, on the other hand, by the fact that they are transmitted according to two patterns which differ in aim relative to one another. It is then possible, simply by measuring the angular deviation of either one of the two responses, and simply by measuring the ratio of the amplitudes of the two responses received, to deduce on the one hand the angular position φ and on the other hand the orientation θ of the mobile. The applications in the automobile sector are numerous (anticollision, control of road traffic and of compliance with the highway code, automatic toll points, etc.).

Optical signal processing in Radar systems

Abstract: Opto-electronic components and their performances are well suited to be integrated in radar systems. In this paper, two optical architectures illustrate functions that are specific to optical processing of microwave signals, i.e., time-delay-based processing and arbitrary waveform generation of large frequency bandwidth signals.

Improving thermal stability of opto-electronic oscillators

Abstract: Stable microwave oscillators are realized based on high-quality factor resonators, which in turn are realized using acoustic, electromagnetic, and optical technologies. This article provides an overview of close-in carrier phase noise and temperature stability of various oscillators

Stimulated Brillouin scattering for microwave signal modulation depth increase in optical links

Abstract: Carrier reduction from a weakly modulated optical signal is required in highly linear optoelectronic links. The proposed solution uses stimulated Brillouin scattering (SBS) that occurs in optical fibres to deplete the carrier and leave the modulation sidebands unchanged. A modulation depth gain of >20 has been obtained using this method.

Spintronics: a spin-based electronics vision for the future.

Abstract: This review describes a new paradigm of electronics based on the spin degree of freedom of the electron. Either adding the spin degree of freedom to conventional charge-based electronic devices or using the spin alone has the potential advantages of nonvolatility, increased data processing speed, decreased electric power consumption, and increased integration densities compared with conventional semiconductor devices. To successfully incorporate spins into existing semiconductor technology, one has to resolve technical issues such as efficient injection, transport, control and manipulation, and detection of spin polarization as well as spin-polarized currents. Recent advances in new materials engineering hold the promise of realizing spintronic devices in the near future. We review the current state of the spin-based devices, efforts in new materials fabrication, issues in spin transport, and optical spin manipulation.

Spintronics: Fundamentals and applications

Abstract: Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics.

Thousandfold Change in Resistivity in Magnetoresistive La-Ca-Mn-O Films

Abstract: A negative isotropic magnetoresistance effect more than three orders of magnitude larger than the typical giant magnetoresistance of some superlattice films has been observed in thin oxide films of perovskite-like La0.67Ca0.33MnOx. Epitaxial films that are grown on LaAIO3 substrates by laser ablation and suitably heat treated exhibit magnetoresistance values as high as 127,000 percent near 77 kelvin and ∼1300 percent near room temperature. Such a phenomenon could be useful for various magnetic and electric device applications if the observed effects of material processing are optimized. Possible mechanisms for the observed effect are discussed.

Why Are There so Few Magnetic Ferroelectrics

Abstract: Multiferroic magnetoelectrics are materials that are both ferromagnetic and ferroelectric in the same phase. As a result, they have a spontaneous magnetization that can be switched by an applied magnetic field, a spontaneous polarization that can be switched by an applied electric field, and often some coupling between the two. Very few exist in nature or have been synthesized in the laboratory. In this paper, we explore the fundamental physics behind the scarcity of ferromagnetic ferroelectric coexistence. In addition, we examine the properties of some known magnetically ordered ferroelectric materials. We find that, in general, the transition metal d electrons, which are essential for magnetism, reduce the tendency for off-center ferroelectric distortion. Consequently, an additional electronic or structural driving force must be present for ferromagnetism and ferroelectricity to occur simultaneously.

Science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems

Abstract: We present the science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems, targeting an evolution in technology, that might lead to impacts and benefits reaching into most areas of society. This roadmap was developed within the framework of the European Graphene Flagship and outlines the main targets and research areas as best understood at the start of this ambitious project. We provide an overview of the key aspects of graphene and related materials (GRMs), ranging from fundamental research challenges to a variety of applications in a large number of sectors, highlighting the steps necessary to take GRMs from a state of raw potential to a point where they might revolutionize multiple industries. We also define an extensive list of acronyms in an effort to standardize the nomenclature in this emerging field.