Spin-momentum locking induced non-local voltage in topological insulator nanowire.

The momentum and spin of charge carriers in the topological insulators are constrained to be perpendicular to each other due to the strong spin-orbit coupling. We have investigated this unique spin-momentum locking property in Sb2Te3 topological insulator nanowires by injecting spin-polarized electrons through magnetic tunnel junction electrodes. Non-local voltage measurements exhibit an asymmetry with respect to the magnetic field applied perpendicular to the nanowire channel, which is remarkably different from that of a non-local measurement in a channel that lacks spin-momentum locking. In stark contrast to conventional non-local spin valves, simultaneous reversal of magnetic moments of all magnetic contacts to the Sb2Te3 nanowire alters the non-local voltage. This unusual asymmetry is a clear signature of the spin-momentum locking in the Sb2Te3 nanowire surface states.

Immunity of nanoscale magnetic tunnel junctions with perpendicular magnetic anisotropy to ionizing radiation.

Spin transfer torque magnetic random access memory (STT-MRAM) is a promising candidate for next generation memory as it is non-volatile, fast, and has unlimited endurance. Another important aspect of STT-MRAM is that its core component, the nanoscale magnetic tunneling junction (MTJ), is thought to be radiation hard, making it attractive for space and nuclear technology applications. However, studies on the effects of ionizing radiation on the STT-MRAM writing process are lacking for MTJs with perpendicular magnetic anisotropy (pMTJs) required for scalable applications. Particularly, the question of the impact of extreme total ionizing dose on perpendicular magnetic anisotropy, which plays a crucial role on thermal stability and critical writing current, remains open. Here we report measurements of the impact of high doses of gamma and neutron radiation on nanoscale pMTJs used in STT-MRAM. We characterize the tunneling magnetoresistance, the magnetic field switching, and the current-induced switching before and after irradiation. Our results demonstrate that all these key properties of nanoscale MTJs relevant to STT-MRAM applications are robust against ionizing radiation. Additionally, we perform experiments on thermally driven stochastic switching in the gamma ray environment. These results indicate that nanoscale MTJs are promising building blocks for radiation-hard non-von Neumann computing.

Injection locking of multiple auto-oscillation modes in a tapered nanowire spin Hall oscillator.

Spin Hall oscillators (SHO) are promising candidates for the generation, detection and amplification of high frequency signals, that are tunable through a wide range of operating frequencies. They offer to be read out electrically, magnetically and optically in combination with a simple bilayer design. Here, we experimentally study the spatial dependence and spectral properties of auto-oscillations in SHO devices based on Pt(7 nm)/Ni80Fe20(5 nm) tapered nanowires. Using Brillouin light scattering microscopy, we observe two individual self-localized spin-wave bullets that oscillate at two distinct frequencies (5.2 GHz and 5.45 GHz) and are localized at different positions separated by about 750 nm within the SHO. This state of a tapered SHO has been predicted by a Ginzburg-Landau auto-oscillator model, but not yet been directly confirmed experimentally. We demonstrate that the observed bullets can be individually synchronized to external microwave signals, leading to a frequency entrainment, linewidth reduction and increase in oscillation amplitude for the bullet that is selected by the microwave frequency. At the same time, the amplitude of other parasitic modes decreases, which promotes the single-mode operation of the SHO. Finally, the synchronization of the spin-wave bullets is studied as a function of the microwave power. We believe that our findings promote the realization of extended spin Hall oscillators accomodating several distinct spin-wave bullets, that jointly cover an extended range of tunability.

[Project to decrease the nasogastric tube occlusion rate in a gastrointestinal unit].

BACKGROUND & PROBLEMS: When oral intake is inadequate or not recommended for patients with underlying diseases or specific treatments, it is common for these patients to receive nutrition enterally through a nasogastric tube. However, tube occlusion is a common complication of enteral feeding tubes. Data collected at our hospital from January to September 2011 identified 7 nasogastric tube occlusion events. All events were resolved by replacing the original tube with a new tube. PURPOSE: The purpose of this project was to reduce the nasogastric tube occlusion rate to 0.31% or less. RESOLUTIONS: Implemented interventions included: 1) developing and administering a course for nurses on nasogastric-tube feeding techniques; (2) providing a filter for powdered medications; (3) developing a standard procedure for administering Nexium through nasogastric tubes; (4) updating patient-education pamphlets for nasogastric tube feeding; and (5) enhancing the quality of nurse auditing on nasogastric tube feeding techniques and nasogastric-tube medication-administration techniques. RESULTS: The average nasogastric tube occlusion rate decreased from 0.76% to 0% and the average nasogastric tube feeding technique compliance rate for nurses increased. The accuracy rate for specific medication administration techniques through nasogastric tubes increased dramatically from 16.7% to 100%. CONCLUSIONS: The project involved a multidisciplinary team of physicians, nurses, and pharmacists. This team developed a standard protocol for nasogastric tube feeding and specific medication administration recommendations for nasogastric tubes; revised nursing practice standards; and decreased the rate of nasogastric tube occlusion.

Control of Schottky barriers in single layer MoS2 transistors with ferromagnetic contacts.

MoS2 and related metal dichalcogenides (MoSe2, WS2, WSe2) are layered two-dimensional materials that are promising for nanoelectronics and spintronics. For instance, large spin-orbit coupling and spin splitting in the valence band of single layer (SL) MoS2 could lead to enhanced spin lifetimes and large spin Hall angles. Understanding the nature of the contacts is a critical first step for realizing spin injection and spin transport in MoS2. Here, we have investigated Co contacts to SL MoS2 and find that the Schottky barrier height can be significantly decreased with the addition of a thin oxide barrier (MgO). Further, we show that the barrier height can be reduced to zero by tuning the carrier density with back gate. Therefore, the MgO could simultaneously provide a tunnel barrier to alleviate conductance mismatch while minimizing carrier depletion near the contacts. Such control over the barrier height should allow for careful engineering of the contacts to realize spin injection in these materials.

Spin relaxation in single-layer graphene with tunable mobility.

Graphene is an attractive material for spintronics due to theoretical predictions of long spin lifetimes arising from low spin-orbit and hyperfine couplings. In experiments, however, spin lifetimes in single-layer graphene (SLG) measured via Hanle effects are much shorter than expected theoretically. Thus, the origin of spin relaxation in SLG is a major issue for graphene spintronics. Despite extensive theoretical and experimental work addressing this question, there is still little clarity on the microscopic origin of spin relaxation. By using organic ligand-bound nanoparticles as charge reservoirs to tune the mobility between 2700 and 12 000 cm(2)/(V s), we successfully isolate the effect of charged impurity scattering on spin relaxation in SLG. Our results demonstrate that, while charged impurities can greatly affect mobility, the spin lifetimes are not affected by charged impurity scattering.

Airway infection predisposes to peristomal infection after percutaneous endoscopic gastrostomy with high concordance between sputum and wound isolates.

BACKGROUND: Peristomal infection is common after percutaneous endoscopic gastrostomy. This study aims to evaluate the correlation between airway and peristomal infected pathogens. METHODS: Before the procedure, sputum cultures were prospectively performed for the patients with airway symptoms. All the patients received prophylactic antibiotics. Once peristomal infection occurred, the wound cultures were obtained to analyze the antibiotic susceptibilities of the pathogens. The paired isolates, with concordance between sputum and wound cultures, were validated for their clone identity using pulsed-field gel electrophoresis. RESULTS: One hundred twelve patients were enrolled, and 30 patients had peristomal infection. The 31 patients with airway pathogens had a 10-fold higher risk of peristomal infection than the other 81 without airway pathogens (95% CI, 3.85-26.4, p < 0.001). Among patients collected with paired isolates from wound and sputum, 85% had concordant microorganism species. In the paired concordant isolates, 94% had indistinguishable antibiogram, and nearly 90% were clonally identical in pulsed-field gel electrophoresis. CONCLUSIONS: Patients with airway infection have an increased risk of peristomal infection after percutaneous endoscopic gastrostomy. Concerning the high concordance between infected wound and sputum isolates of such patients, the selection of appropriate prophylactic antibiotics could be individual to cover the microorganisms isolated from sputum.