Realizing a high magnetic moment in Gd/Cr/FeCo: The role of the rare earth

The search for materials or systems exhibiting a high magnetic saturation has been of longstanding importance. It has been suggested that increased saturation could be achieved by coupling a transition metal via a spacer to a rare earth. We report Gd/Cr/Fe₇₀Co₃₀ multilayer stacks and find reduced yet modulating magnetic moment as a function of Cr thickness. Through a micro structural analysis the lowered moment is indicated by the nucleation of the ultrathin Gd films into an fcc phase. We discuss the possible solution in terms of quasi-perfect lattice match seed material to promote growth of hcp Gd.

Le thème du mensonge dans Le Petit Canard de Jacques Laurent’

ADEFFI annual conference
Trinity College Dublin
October 2007

Characteristics of Transverse Waves in Chromospheric Mottles

Using data obtained by the high temporal and spatial resolution Rapid Oscillations in the Solar Atmosphere instrument on the Dunn Solar Telescope, we investigate at an unprecedented level of detail transverse oscillations in chromospheric fine structures near the solar disk center. The oscillations are interpreted in terms of propagating and standing magnetohydrodynamic kink waves. Wave characteristics including the maximum transverse velocity amplitude and the phase speed are measured as a function of distance along the structure's length. Solar magnetoseismology is applied to these measured parameters to obtain diagnostic information on key plasma parameters (e.g., magnetic field, density, temperature, flow speed) of these localized waveguides. The magnetic field strength of the mottle along the ~2 Mm length is found to decrease by a factor of 12, while the local plasma density scale height is ~280 ± 80 km.

Influence of strain and polycrystalline ordering on magnetic properties of high moment rare earth metals and alloys

Despite being the most suitable candidates for solenoid pole pieces in state-of-the-art superconductor- based electromagnets, the intrinsic magnetic properties of heavy rare earth metals and their alloys have gained comparatively little attention. With the potential of integration in micro- and nanoscale devices, thin films of Gd, Dy, Tb, DyGd and DyTb were plasma-sputtered and investigated for their in-plane magnetic properties, with an emphasis on magnetisation vs. temperature profiles. Based on crystal structure analysis of the polycrystalline rare earth films, which consist of a low magnetic moment FCC layer at the seed interface topped with a higher moment HCP layer, an experimental protocol is introduced which allows the direct magnetic analysis of the individual layers. In line with the general trend of heavy lanthanides, the saturation magnetisation was found to drop with increasing unit cell size. In-situ annealed rare earth films exceeded the saturation magnetisation of a high-moment Fe65Co35 reference film in the cryogenic temperature regime, proving their potential for pole piece applications; however as-deposited rare earth films were found completely unsuitable. In agreement with theoretical predictions, sufficiently strained crystal phases of Tb and Dy did not exhibit an incommensurate magnetic order, unlike their single-crystal counterparts which have a helical phase. DyGd and DyTb alloys followed the trends of the elemental rare earth metals in terms of crystal structure and magnetic properties. Inter-rare-earth alloys hence present a desirable blend of saturation magnetisation and operating temperature.

Cockney, pseudo-slang et argot de série noire : San-Antonio et le moment Peter Cheyney du roman noir français

This article examines how in post-war France slang became a byword for the noir genre. It considers the mechanisms, models, networks and translators' practices which set the tone for the "Série Noire”, whose influence, both written and on the screen, had, within a decade, become, a "mythology" studied by Roland Barthes. It argues that this use of slang is redolent of the inauthenticity which characterises this stage in the reception of the Noir genre in France. It is certain that this artificial French slang is far from devoid of charm, or even mystery. But it tends to depreciate and deform the translated works and seems to be the hallmark of an era that might have defined and acclimatised Noir fiction in France, yet remains one which has not fully understood the gravity of its purpose. While such translations seem outdated nowadays (if not quite incomprehensible ), original works written at the time in French by writers inspired by the model of " pseudo- slang" and the fashionability of American popular culture have benefited from them. In this very inauthenticity, derivative novels have found a licence for invention and freedom, with authors such as Cocteau hailing it as a revival of the French written language. We see here how the adventures of Commissaire San Antonio, by Frédéric Dard constitute the best examples of this new creativity in French and draw upon a template set for the reception of American literature

A review of high magnetic moment thin films for microscale and nanotechnology applications

The creation of large magnetic fields is a necessary component in many technologies, ranging from magnetic resonance imaging, electric motors and generators, and magnetic hard disk drives in information storage. This is typically done by inserting a ferromagnetic pole piece with a large magnetisation density MS in a solenoid. In addition to large MS, it is usually required or desired that the ferromagnet is magnetically soft and has a Curie temperature well above the operating temperature of the device. A variety of ferromagnetic materials are currently in use, ranging from FeCo alloys in, for example, hard disk drives, to rare earth metals operating at cryogenic temperatures in superconducting solenoids. These latter can exceed the limit on MS for transition metal alloys given by the Slater-Pauling curve. This article reviews different materials and concepts in use or proposed for technological applications that require a large MS, with an emphasis on nanoscale material systems, such as thin and ultra-thin films. Attention is also paid to other requirements or properties, such as the Curie temperature and magnetic softness. In a final summary, we evaluate the actual applicability of the discussed materials for use as pole tips in electromagnets, in particular, in nanoscale magnetic hard disk drive read-write heads; the technological advancement of the latter has been a very strong driving force in the development of the field of nanomagnetism.

Transverse Spreading of Electrons in High-Intensity Laser Fields

We show that for collisions of electrons with a high-intensity laser, discrete photon emissions introduce a transverse beam spread that is distinct from that due to classical (or beam shape) effects. Via numerical simulations, we show that this quantum induced transverse momentum gain of the electron is manifest in collisions with a realistic laser pulse of intensity within reach of current technology, and we propose it as a measurable signature of strong-field quantum electrodynamics.

Finite element modelling of cyclic behaviour of cold-formed steel bolted moment-resisting connections

This paper investigates the accuracy of new finite element modelling approaches to predict the behaviour of bolted moment-connections between cold-formed steel members, formed by using brackets bolted to the webs of the section, under low cycle fatigue. ABAQUS software is used as a modelling platform. Such joints are used for portal frames and potentially have good seismic resisting capabilities, which is important for construction in developing countries. The modelling implications of a two-dimensional beam element model, a three-dimensional shell element model and a three-dimensional solid element model are reported. Quantitative and qualitative results indicate that the three-dimensional quadratic S8R shell element model most accurately predicts the hysteretic behaviour and energy dissipation capacity of the connection when compared to the test results.

Development of Seismic Fragility Functions for a Moment Resisting Reinforced Concrete Framed Structure

Understanding the seismic vulnerability of building structures is important for seismic engineers, building owners, risk insurers and governments. Seismic vulnerability defines a buildings predisposition to be damaged as a result of an earthquake of a given severity. There are two components to seismic risk; the seismic hazard and the exposure of the structural inventory to any given earthquake event. This paper demonstrates the development of fragility curves at different damage states using a detailed mechanical model of a moment resisting reinforced concrete structure typical of Southern Europe. The mechanical model consists of a complex three-dimensional finite element model of the reinforced concrete moment resisting frame structure and is used to define the damage states through pushover analysis. Fragility curves are also defined using the HAZUS macroseismic methodology and the Risk-UE macroseismic methodology. Comparison of the mechanically modelled and HAZUS fragility curve shows good agreement while the Risk-UE methodology shows reasonably poor agreement.

Selective Multi-Carrier Index Keying OFDM: Error Propagation Rate with Moment Generating Function

We propose a new selective multi-carrier index keying in orthogonal frequency division multiplexing (OFDM) systems that opportunistically modulate both a small subset of sub-carriers and their indices. Particularly, we investigate the performance enhancement in two cases of error propagation sensitive and compromised deviceto-device (D2D) communications. For the performance evaluation, we focus on analyzing the error propagation probability (EPP) introducing the exact and upper bound expressions on the detection error probability, in the presence of both imperfect and perfect detection of active multi-carrier indices. The average EPP results in closedform are generalized for various fading distribution using the moment generating function, and our numerical results clearly show that the proposed approach is desirable for reliable and energy-efficient D2D applications.