First principle energies of binary and ternary phases of the Fe–Nb–Ni–Cr system

We present first principles enthalpies of formation and lattice parameters of iron, nickel, chromium and niobium alloys. Some of these results have been partially used in a recent assessment of the Fe–Ni–Cr–Nb quaternary phase diagram. Emphasis has been put on the fcc (A1) and bcc (A2) unary structures, the X3Y-D022, -L12, -D03, -D0a, X2Y-C14(MgZn2), -C15(MgCu2) and -C36 (MgNi2) Laves and X7Y6-D85 (μ) binary phases, and the X8Y4Z18-D8b (σ) ternary phase. We employed the state of the art to compute their properties by means of the DFT (PBE functional and PAW pseudo potentials). A comparison with experimental and theoretical data is also provided

Theory of Spin-Transfer Torque in the Current-in-Plane Geometries

Two alternative current-induced switching geometries, in which the current flows parallel to the magnet/nonmagnet interface, are investigated theoretically using the nonequilibrium Keldysh theory. In the first geometry, the current is perpendicular to the polarizing magnet/nonmagnet interface but parallel to the nonmagnet/switching magnet interface (CPIP). In the second geometry, the current is parallel to both the polarizing magnet/nonmagnet and nonmagnet/switching magnet interfaces (CIP). Calculations for a single-orbital tight binding model indicate that the spin current flowing parallel to the switching magnet/nonmagnet interface can be absorbed by a lateral switching magnet as efficiently as in the traditional current-perpendicular-to-plane (CPP) geometry. The results of the model calculations are shown to be valid also for experimentally relevant Co/Cu CPIP system described by fully realistic tight binding bands fitted to an ab initio band structure. It is shown that almost complete absorption of the incident spin current by a lateral switching magnet occurs when the lateral dimensions of the switching magnet are of the order of 50-100 interatomic distances, i.e., about 20nm and its height as small as a few atomic planes. It is also demonstratedthat strong spin current absorption in the CPIP/CIP geometry is not spoilt by the presence of a rough interface between the switching magnet and nonmagnetic spacer. Polarization achieved using a lateral magnet in the CIP geometry is found to be about 25% of that in the traditional CPP geometry. The present CPIP calculations of the spin transfer torque are also relevant to the so called pure-spin-current-induced magnetization switching that had been recently observed.Comment: 9 pages 8 figure

Alien Registration- Mathon, Bernadette (Lewiston, Androscoggin County)

https://digitalmaine.com/alien_docs/28948/thumbnail.jp

Alien Registration- Mathon, Ernest (Lewiston, Androscoggin County)

https://digitalmaine.com/alien_docs/28949/thumbnail.jp

Alien Registration- Mathon, Wilfred (Lewiston, Androscoggin County)

https://digitalmaine.com/alien_docs/28951/thumbnail.jp

A (49,16,3,6) strongly regular graph does not exist

Graphs;mathematics

Systematic Two-band Model Calculations of the GMR Effect with Metallic and Nonmetallic Spacers and with Impurities

By an accurate Green's function method we calculate conductances and the corresponding Giant Magneto-Resistance effects (GMR) of two metallic ferromagnetic films separated by different spacers, metallic and non-metallic ones, in a simplified model on a sc lattice, in CPP and CIP geometries (i.e. current perpendicular or parallel to the planes), without impurities, or with interface- or bulk impurities. The electronic structure of the systems is approximated by two hybridized orbitals per atom, to mimic s-bands and d-bands and their hybridization. We show that such calculations usually give rough estimates only, but of the correct order of magnitude; in particular, the predictions on the impurity effects depend strongly on the model parameters. One of our main results is the prediction of huge CPP-GMR effects for {\it non-metallic} spacers in the ballistic limit.Comment: Revised version; discussions and references improved; accepted by JMM

La tribune peinte de l'église Sainte-Eulalie de Millas: étude technique et conservation

La réalisation de la tribune de l'église de Millas est bien documentée entre 1440 et 1442. Sa grande originalité réside dans la présence de 52 têtes sculptées et polychromes et de 13 armoiries différentes répétées à 132 reprises qui correspondent probablement aux personnes ayant participé à son financement. Elle est composée de 26 poutres, 104 corbeaux, 156 closoirs et 104 caissons sculptés. Différentes interventions par le passé ont contribué à endommager la structure, mais surtout la polychromie. Une intervention de restauration est nécessaire afin de reprendre les assemblages, consolider le bois, refixer la polychromie et éliminer les restes de repeints