Omar U. Need

Differential scanning calorimetric study of the Transition heats of some dibenzazepines, carbazoles and phenothiazines

Abstract The transition temperatures and heats of two dibenzazepines, three carbazoles and three phenothiazines have been obtained. This represents a continuation of an earlier study of a series of acyldibenzazepines. Additional evidence for a back-folded acylchain in the solid state has been developed and good correlation of these bent ring molecules with well known spherical molecules on the basis of transition entropy is possible. The behaviour of the alkyl chain in acyl substituted dibenzazepines, carbazoles and phenothiazines is contrasted with other alkyl substituted ring systems.

Direct measurement of spin dependent mean free paths in metals (abstract)

We describe results obtained using a new spin valve structure that is specifically designed to measure the spin up and spin down mean free paths in ferromagnetic metals. We report how these mean free paths can be measured more directly and with greater accuracy than previous methods, which were based mostly on indirect evidence from magnetoresistance in ternary alloys. The technique is based on the ‘‘backed’’ spin valve layered structure: substrate/seed/80 A FeMn/50 A NiFe/23 A Cu/20 A NiFe/t A b/50 A Ta where the back layer of material b with thickness t is probed by the rest of the structure, which forms a spin polarized conduction electron source. As t is varied the majority carrier mean free path λ+b in the layer b is obtained directly from the form taken by the change in film conductance between parallel and antiparallel magnetization states, ΔG, whose solution of the Boltzmann transport equation shows is well approximated by the form ΔG=ΔG0+ΔGb{1−exp([t−tx]/βλ+b)}, where ΔG0 arises from the 20 A NiF...