Current-driven dynamics of chiral ferromagnetic domain walls

In most ferromagnets the magnetization rotates from one domain to the next with no preferred handedness. However, broken inversion symmetry can lift the chiral degeneracy, leading to topologically-rich spin textures such as spin-spirals and skyrmions via the Dzyaloshinskii-Moriya interaction (DMI). Here we show that in ultrathin metallic ferromagnets sandwiched between a heavy metal and an oxide, the DMI stabilizes chiral domain walls (DWs) whose spin texture enables extremely efficient current-driven motion. We show that spin torque from the spin Hall effect drives DWs in opposite directions in Pt/CoFe/MgO and Ta/CoFe/MgO, which can be explained only if the DWs assume a N\'eel configuration with left-handed chirality. We directly confirm the DW chirality and rigidity by examining current-driven DW dynamics with magnetic fields applied perpendicular and parallel to the spin spiral. This work resolves the origin of controversial experimental results and highlights a new path towards interfacial design of spintronic devices

Fiscal and Monetary Policy and its Effect on the Growth of Nigeria Economy

The study examined the empirical link on the effect of fiscal and monetary policy on the Economic Growth of Nigeria (1986-2010). The objectives were to determine factors of fiscal and monetary policy that contributed to the growth of Nigeria economy. It made use of secondary data, from Central Bank of Nigeria statistical Bulletin, Volume 21, 2010 and employed the ordinary least squares method of statistical analysis. It was found out that government revenue had a positive impact and statistical significant on gross domestic product. Also shown that government expenditure was positively significant on the growth of Nigeria Economy. The second model depicts that money supply had a positive impact on gross domestic product and it discovered that this variable was statistically significant. Exchange rate variable had a positive impact on the performance of Nigeria economy. The finding revealed that inflation had a positive impact but there was no significant relationship between inflation and gross domestic product. It therefore suggests that government should increase the number of fiscal policy instruments over and above the ones currently in use. The study recommended that measures should be adopted that would ensure income generation and government revenue generating ventures. Keywords: Balance of payment, Economic growth, Exchange rate, Government expenditure, Inflation, Money supply

Large voltage-induced modification of spin-orbit torques in Pt/Co/GdOx

We report on large modifications of current-induced spin-orbit torques in a gated Pt/Co/Gd-oxide microstrip due to voltage-driven O$^{2-}$ migration. The Slonczewski-like and field-like torques are quantified using a low-frequency harmonic technique based on the polar magneto-optical Kerr effect. Voltage-induced oxidation of Co enhances the Slonczewski-like torque by as much as an order of magnitude, and simultaneously reduces the anisotropy energy barrier by a factor of ~5. Such magneto-ionic tuning of interfacial spin-orbit effects may significantly enhance the efficiency of magnetization switching and provide additional degrees of freedom in spintronic devices

An Advanced Control Strategy for the Evaporation Section of An Integrated First- and Second-Generation Ethanol Sugarcane Biorefinery

The sugarcane crushing stage is one of the most important technologies being developed at the moment. In this paper, the control of the multiple-stage evaporation system was addressed, as it is a crucial stage in the first- and second-generation ethanol production from sugarcane. A neural network model was proposed based on a dynamic phenomenological model developed in EMSO (Environment for Modeling, Simulation and Optimization). The phenomenological model was used to build a neural network prediction model for an MPC (Model Predictive Control) scheme using a DMC (Dynamic Matrix Control) algorithm. Simulations were carried out to evaluate the performance for tracking the set-point. Also, disturbance rejection tests were performed, considering different step disturbances. The analysis demonstrated that the MPC scheme performed well in the tests and showed superiority when compared to classical PID controllers. This work is licensed under a Creative Commons Attribution 4.0 International License

Chiral magnetization textures stabilized by the Dzyaloshinskii-Moriya interaction during spin-orbit torque switching

We study the effect of the Dzyaloshinskii-Moriya interaction (DMI) on current-induced magnetic switching of a perpendicularly magnetized heavy-metal/ferromagnet/oxide trilayer both experimentally and through micromagnetic simulations. We report the generation of stable helical magnetization stripes for a sufficiently large DMI strength in the switching region, giving rise to intermediate states in the magnetization confirming the essential role of the DMI on switching processes. We compare the simulation and experimental results to a macrospin model, showing the need for a micromagnetic approach. The influence of the temperature on the switching is also discussed.Comment: Includes corrected acknowledgements and clarification of simulation parameter

Spin Hall torque magnetometry of Dzyaloshinskii domain walls

Current-induced domain wall motion in the presence of the Dzyaloshinskii-Moriya interaction (DMI) is experimentally and theoretically investigated in heavy-metal/ferromagnet bilayers. The angular dependence of the current-induced torque and the magnetization structure of Dzyaloshinskii domain walls are described and quantified simultaneously in the presence of in-plane fields. We show that the DMI strength depends strongly on the heavy metal, varying by a factor of 20 between Ta and Pa, and that strong DMI leads to wall distortions not seen in conventional materials. These findings provide essential insights for understanding and exploiting chiral magnetism for emerging spintronics applications

Generalized analysis of thermally activated domain-wall motion in Co/Pt multilayers

Thermally activated domain-wall (DW) motion driven by magnetic field and electric current is investigated experimentally in out-of-plane magnetized Pt(Co/Pt)$_3$ multilayers. We directly extract the thermal activation energy barrier for DW motion and observe the dynamic regimes of creep, depinning, and viscous flow. Further analysis reveals that the activation energy must be corrected with a factor dependent on the Curie temperature, and we derive a generalized Arrhenius-like equation governing thermally activated motion. By using this generalized equation, we quantify the efficiency of current-induced spin torque in assisting DW motion. Current produces no effect aside from Joule heating in the multilayer with 7-\AA\ thick Co layers, whereas it generates a finite spin torque on DWs in the multilayer with atomically thin 3-\AA\ Co layers. These findings suggest that conventional spin-transfer torques from in-plane spin-polarized current do not drive DWs in ultrathin Co/Pt multilayers

Women's knowledge of maternal danger signs during pregnancy: Findings from a cross-sectional survey in Papua New Guinea

© 2019 Objective: To explore knowledge of pregnancy related danger signs among women attending antenatal clinics in Papua New Guinea. Design: Cross-sectional survey undertaken as part of a wider integrated health and demographic survey. Setting: Three sites in Papua New Guinea: Hiri District (Central Province), Karkar (Madang Province) and Asaro (Eastern Highlands Province). Participants: 482 women aged 15–44 years. Findings: Almost all (95.2%; 459/482) women attended for antenatal care at least once; 68.2% attended four or more times. Among women who attended the antenatal clinic, 53.6% (246/459) reported receiving information about danger signs in pregnancy from a health worker. Of these 60.2% (148/246) could recall at least one danger sign. In addition, 16.4% (35/213) of women who did not receive information from the antenatal clinic reported pregnancy related danger signs. Among the 183 women who reported danger signs, 47.5% (87/183) reported fever; 39.3% (72/183) reported vaginal bleeding and 36.6% (67/183) reported swelling of the face, legs and arms. Women who reported receiving information at the antenatal clinic were significantly more likely know any danger signs, compared with women who did not receive information at the antenatal clinic (OR 7.68 (95%CI: 4.93, 11.96); p = <0.001). Knowledge of danger signs was significantly associated with secondary school education, compared with none or only primary education (OR 3.08 (95% CI: 2.06, 4.61); p = <0.001). Conclusions and implications for practice: Every antenatal clinic visit should be used opportunistically to provide women with information about key danger signs during pregnancy and childbirth. Recognising maternal danger signs, together with the importance of seeking early transfer to the health facility and the importance of attending for a health facility birth are critical to improving outcomes for mothers and babies especially in low income settings such as Papua New Guinea