Second Annual CMDC Conference, on the Theme of Environment-compatible Energy-sources, held at the Hotel Zürich, Zürich, Switzerland, during 10-12 December 1990

PAS 1109,EE 1108 PHYSIC

Dependence of spin pumping and spin transfer torque upon Ni81Fe19 thickness in Ta/Ag/Ni81Fe19/Ag/Co2MnGe/Ag/Ta spin-valve structures

This is the final version of the article. Available from American Physical Society via the DOI in this record.Spin pumping has been studied within Ta / Ag / Ni 81 Fe 19 (0–5 nm) / Ag (6 nm) / Co 2 MnGe (5 nm) / Ag / Ta large-area spin-valve structures, and the transverse spin current absorption of Ni 81 Fe 19 sink layers of different thicknesses has been explored. In some circumstances, the spin current absorption can be inferred from the modification of the Co 2 MnGe source layer damping in vector network analyzer ferromagnetic resonance (VNA-FMR) experiments. However, the spin current absorption is more accurately determined from element-specific phase-resolved x-ray ferromagnetic resonance (XFMR) measurements that directly probe the spin transfer torque (STT) acting on the sink layer at the source layer resonance. Comparison with a macrospin model allows the real part of the effective spin mixing conductance to be extracted. We find that spin current absorption in the outer Ta layers has a significant impact, while sink layers with thicknesses of less than 0.6 nm are found to be discontinuous and superparamagnetic at room temperature, and lead to a noticeable increase of the source layer damping. For the thickest 5-nm sink layer, increased spin current absorption is found to coincide with a reduction of the zero frequency FMR linewidth that we attribute to improved interface quality. This study shows that the transverse spin current absorption does not follow a universal dependence upon sink layer thickness but instead the structural quality of the sink layer plays a crucial role.The authors gratefully acknowledge the support of EPSRC Grant No. EP/J018767/1, and the award of the Exeter-Brown Scholarship in High Frequency Spintronics to C.J.D

Painlev\'e structure of a multi-ion electrodiffusion system

A nonlinear coupled system descriptive of multi-ion electrodiffusion is investigated and all parameters for which the system admits a single-valued general solution are isolated. This is achieved \textit{via} a method initiated by Painleve' with the application of a test due to Kowalevski and Gambier. The solutions can be obtained explicitly in terms of Painleve' transcendents or elliptic functions.Comment: 9 p, Latex, to appear, J Phys A FT

The Rate of the Photoelectrochemical Generation of Hydrogen at p-Type Semiconductors

The current-potential relations with and without illumination, quantum efficiency-wavelength relations at several potentials, the flatband potentials, the transient behavior, and the stability of seven p-type semiconductors, i.e., ZnTe, CdTe, GaAs, InP, GaP, SiC, and Si, have been measured in 1N NaOH and 1N H2SO4. The position of the photocurrent-potential relations are related to the flatband potential and the energy gap of the semiconductor. The existence of the maximum in quantum efficiency-wavelength relation is analyzed by considering surface recombination. The stability and the transient behavior are analyzed

The Theory of the Light-Induced Evolution of Hydrogen at Semiconductor Electrodes

The photoelectrode kinetics of the hydrogen evolution reaction is considered, using the WKB approximation for the penetration of the barrier at the semiconductor-solution interface. The absorption characteristics of photons in the eIectrode are introduced and the number of electrons produced at the surface is obtained as a function of the semiconductor statistics, and also diffusion and field effects. The model makes use of the conclusion that the photo-produced electrons have been deactivated to the bottom of the conduction band by the time they have diffused from the point of photon absorption to the surface. Image energy and the potential difference in the double layer at the semiconductor-solution interface are taken into account. The expression obtained for the photo hydrogen current density is tested in its ability to predict the photo-current-potential curves at the gallium phosphide cathode. Agreement with experiment is fair. Discrepancies are discussed