Suppression of spin-pumping by a MgO tunnel-barrier

Spin-pumping generates pure spin currents in normal metals at the ferromagnet (F)/normal metal (N) interface. The efficiency of spin-pumping is given by the spin mixing conductance, which depends on N and the F/N interface. We directly study the spin-pumping through an MgO tunnel-barrier using the inverse spin Hall effect, which couples spin and charge currents and provides a direct electrical detection of spin currents in the normal metal. We find that spin-pumping is suppressed by the tunnel-barrier, which is contrary to recent studies that suggest that the spin mixing conductance can be enhanced by a tunnel-barrier inserted at the interface

Manned Versus Unmanned Aircraft Accidents, Including Causation and Rates

Many consider aircraft reliability a primary deterrent to the further integration of unmanned aircraft into civil airspace. Discussions of unmanned aircraft reliability often include comparisons of accident rates of medium and large unmanned aircraft (like the MQ-1 Predator and MQ-9 Reaper) to those of manned aircraft. These comparisons, however, often consider a recent period only but do not consider platform maturity. While this approach is valid—and worthy of discussion—it does not present a complete picture of the unmanned aircraft safety record. This paper employs a chi-square goodness-of-fit approach to compare the progression of the U.S. Air Force MQ-9 mishap rate to that of six manned aircraft flown by the same service. The analysis found that the MQ-9 did not have a significantly different Class A mishap rate progression from the comparison aircraft. The only exception was the F-16, which had a considerably higher rate. In addition, to better understand mishap causation, a comparison of manned to unmanned aircraft mishap causal factors was conducted, primarily relying on journal articles that use the Human Factors and Classification System (HFACS) taxonomy. The analysis found that, like manned aircraft, crew errors contributed to a significant portion of unmanned aircraft accidents, and further, that skill-based errors were often the type of the crew error. The studies also indicated that increasing autonomous control, Human Machine Interface (HMI) design, and crew training will continue to play a significant role in unmanned aircraft mishap causation. Two case studies were also analyzed to highlight differences in manned and unmanned aircraft accident causation

In-situ measurement of the permittivity of helium using microwave NbN resonators

By measuring the electrical transport properties of superconducting NbN quarter-wave resonators in direct contact with a helium bath, we have demonstrated a high-speed and spatially sensitive sensor for the permittivity of helium. In our implementation a $\sim10^{-3}$ mm$^3$ sensing volume is measured with a bandwidth of 300 kHz in the temperature range 1.8 to 8.8 K. The minimum detectable change of the permittivity of helium is calculated to be $\sim6\times$$10^{-11}$ $\epsilon_0$/Hz$^{1/2}$ with a sensitivity of order $10^{-13}$ $\epsilon_0$/Hz$^{1/2}$ easily achievable. Potential applications include operation as a fast, localized helium thermometer and as a transducer in superfluid hydrodynamic experiments.Comment: 4 pages, 3 figure

Detection and quantification of inverse spin Hall effect from spin pumping in permalloy/normal metal bilayers

Spin pumping is a mechanism that generates spin currents from ferromagnetic resonance (FMR) over macroscopic interfacial areas, thereby enabling sensitive detection of the inverse spin Hall effect that transforms spin into charge currents in non-magnetic conductors. Here we study the spin-pumping-induced voltages due to the inverse spin Hall effect in permalloy/normal metal bilayers integrated into coplanar waveguides for different normal metals and as a function of angle of the applied magnetic field direction, as well as microwave frequency and power. We find good agreement between experimental data and a theoretical model that includes contributions from anisotropic magnetoresistance (AMR) and inverse spin Hall effect (ISHE). The analysis provides consistent results over a wide range of experimental conditions as long as the precise magnetization trajectory is taken into account. The spin Hall angles for Pt, Pd, Au and Mo were determined with high precision to be $0.013\pm0.002$, $0.0064\pm0.001$, $0.0035\pm0.0003$ and $-0.0005\pm0.0001$, respectively.Comment: 11 page

Fourth Annual Report: Agricultural Sector Analysis in Thailand

This Fourth Annual Report summarizes accomplishments of the Agricultural Sector Analysis Project in Thailand during fiscal year 1977 and relates these accomplishments to past work progress as well as to projected work for fiscal year 1978. Accomplishments described in this report are a result of the cooperative research effort being carried out by the Division of Agricultural Economics (DAE) of the Ministry of Agriculture and Cooperatives, Royal Thai Government, and the Center for Agricultural and Rural Development of Iowa State University. The cooperative research effort is funded by the United States Agency for International Development and the Royal Thai Government. This summary describes one phase of a sector analysis project being undertaken to provide models and empirical analysis which can aid development and policies for agriculture in Thailand.https://lib.dr.iastate.edu/dae-card_sectoranalysis/1011/thumbnail.jp

Low-voltage nanodomain writing in He-implanted lithium niobate crystals

A scanning force microscope tip is used to write ferroelectric domains in He-implanted single-crystal lithium niobate and subsequently probe them by piezoresponse force microscopy. Investigation of cross-sections of the samples showed that the buried implanted layer, $\sim 1$\,\textmu m below the surface, is non-ferroelectric and can thus act as a barrier to domain growth. This barrier enabled stable surface domains of $< 1$\,\textmu m size to be written in 500\,\textmu m-thick crystal substrates with voltage pulses of only 10\,V applied to the tip