Time-resolved spin-torque switching and enhanced damping in permalloy/Cu/permalloy spin-valve nanopillars

We report time-resolved measurements of current-induced reversal of a free magnetic layer in Permalloy/Cu/Permalloy elliptical nanopillars at temperatures T=4.2 K to 160 K. Comparison of the data to Landau-Lifshitz-Gilbert macrospin simulations of the free layer switching yields numerical values for the spin torque and the Gilbert damping parameters as functions of T. The damping is strongly T dependent, which we attribute to the presence of an antiferromagnetic oxide layer around the perimeter of the Permalloy free layer. This adventitious antiferromagnetic oxide can have a major impact on spin-torque phenomena.     

Electronic and Structural High Pressure Properties of CuGaS 2 Chalcopyrite Semiconductor

We have investigated high-pressure structural properties and ab-initio band structure calculations of the ternary CuGaS 2 by single crystal X-ray diffraction up to 8 GPa. The single crystal X-ray diffraction experiments were performed in a Merrill-Bassett diamond anvil cell. The analysis of the X-ray data makes possible the accurate determination of the atomic position of the unit cell under pressure. The structural parameter u and the Cu-S and Ga-S bond lengths have been deduced. The results of the electronics band structure calculation using a first-principles pseudo-potential method and the local density approximation (LDA) are reported. The pressure derivatives of the energy gap are calculated and the values are in reasonable good agreement with the experimental ones.     

SPRITE MRI of bubbly flow in a horizontal pipe

Bubble flow is characterised by numerous phase interfaces and turbulence, leading to fast magnetic resonance signal decay and artefacts in spin-warp imaging. In this paper, the SPRITE MRI pulse sequence, with its potential for very short encoding times, is demonstrated as an ideal technique for studying such dynamic systems. It has been used to acquire liquid velocity and relative intensity maps of two-phase gas–liquid dispersed bubble flow in a horizontal pipe at a liquid Reynolds number of 14,500. The fluids were air and water and a turbulence grid was used to generate a dispersed bubble flow pattern. The SPRITE technique shows promise for future research in gas–liquid flow.     

An improved synthesis of the hexaruthenium carbido cluster Ru6C(CO)17; X-ray structure of the salt [Ph4As]2[Ru6C(CO)16]

Reaction of ethylene with Ru₃(CO)₁₂ under conditions of moderate pressure and temperature gives Ru₆C(CO)₁₇ (I) in ca. 70% yield. Reaction of this carbonyl carbido species with base gives the dianion [Ru₆C(CO)₁₆]^2? ; X-ray analysis of the [Ph₄As]⁺ salt indicates an octahedral array of metal atms with the carbon at the centre of the octahedron and twelve terminal and four edge bridging carbonyl ligands giving an approximate overall C_2v symmetry.     

The production of ions for single-ion traps

A new method of obtaining ions for electrodynamic traps at high vacuum is described, in which an oven produces both a beam of neutral atoms and an electron beam with which to ionize the atoms within the confinement volume of a trap.     

Cyclic adrenaline derivatives. Aryl-2-Piperidyl-Carbinols

A synthetic route; to 3,4-dihydroxyphenyl-(2-piperidyl)earbinols is described. These novel catecholamines may be regarded as derivatives of adrenaline containing a cyclic side-chain moiety. Their biological action appears to be more selective than that of adrenaline or isoprenaline and the more active of these compounds show promise as powerful bronchodilators with minimum cardiac effect.     

Temperature dependence of spin-transfer-induced switching of nanomagnets

We measure the temperature, magnetic-field, and current dependence for the switching of nanomagnets by a spin-polarized current. Depending on current bias, switching can occur between either two static magnetic states or a static state and a current-driven precessional mode. In both cases, the switching is thermally activated and governed by the sample temperature, not a higher effective magnetic temperature. The activation barriers for switching between static states depend linearly on current, with a weaker dependence for dynamic to static switching.     

Conduction switching of photochromic molecules

We report a theoretical study of single molecule conduction switching of photochromic dithienylethene molecules. The light-induced intramolecular transformation drives a swapping of the highest occupied molecular orbital and lowest unoccupied molecular orbital between two distinct conjugated paths. The shuffling of single and double bonds produces a significant conductance change when the molecule is sandwiched between metal electrodes. We model the switching event using quantum molecular dynamics and the conductance changes using Green's function electronic transport theory. We find large on-off conductance ratios (between 10 and over 100) depending on the side group outside the switching core.