Spin transport with traps: dramatic narrowing of the Hanle curve

We study theoretically the spin transport in a device in which the active layer is an organic film with numerous deep in-gap levels serving as traps. A carrier, diffusing between magnetized injector and detector, spends a considerable portion of time on the traps. This new feature of transport does not affect the giant magnetoresistance, which is sensitive only to the mutual orientation of magnetizations of the injector and detector. By contrast, the presence of traps strongly affects the sensitivity of the spin transport to external magnetic field perpendicular to the magnetizations of the electrodes (the Hanle effect). Namely, the Hanle curve narrows dramatically. The origin of such a narrowing is that the spin precession takes place during the entire time of the carrier motion between the electrodes, while the spin relaxation takes place only during diffusive motion between the subsequent traps. If the resulting width of the Hanle curve is smaller than the measurement resolution, observation of the Hanle peak becomes impossible.Comment: 5 pages, 3 figure

Heuristic Computation of Periodic-Review Base Stock Inventory Policies

Heuristic Computation of Periodic-Review Base Stock Inventory Policie

Temperature dependence of the spin relaxation in highly degenerate ZnO thin films

Zinc oxide is a wide-bandgap semiconductor which is considered a potential candidate for fabricating next-generation transparent spintronic devices. However, before this can be practically achieved, a thorough, scientific understanding of the various spin transport and relaxation processes undergone in this material is essential. In the present paper we report our investigations into these processes via temperature dependent, non-local Hanle experiments. Epitaxial ZnO thin films were deposited on c-axis sapphire substrates using a pulsed laser deposition technique. Careful structural, optical, and electrical characterizations of the films were performed. Temperature dependent Hanle measurements were carried out, using an all-electrical scheme for spin injection and detection, in a non-local geometry over the temperature range of 20 - 300 K. Carrier concentration in these films, as determined by Hall effect measurements, was found to be of the order of 10^19 cm^-3. It was determined that in such a degenerately doped system it is essential to use Fermi-Dirac statistics to explain the transport of carriers in the system. From the Hanle data, spin relaxation time in the ZnO films was determined at different temperatures. Our analysis of the temperature-dependent spin relaxation time data suggests that the dominant mechanism of spin relaxation in ZnO films is the Dyakonov-Perel (DP) mechanism modified for the wurtzite crystalline structure in which a hexagonal c-axis reflection asymmetry is present. As a result of this modification the spin-relaxation rate is linear-in-momentum.Comment: 19 pages, 5 figure

Improving Forecast Accuracy by Combination

Improving Forecast Accuracy by Combinatio