When an electron moves in a smoothly varying non-collinear magnetic structure, its spin-orientation adapts constantly, thereby inducing forces that act on both the magnetic structure and the electron. These forces may be described by electric and magnetic fields of an emergent electrodynamics. The topologically quantized winding number of so-called skyrmions, i.e., certain magnetic whirls, discovered recently in chiral magnets are theoretically predicted to induce exactly one quantum of emergent magnetic flux per skyrmion. A moving skyrmion is therefore expected to induce an emergent electric field following Faraday's law of induction, which inherits this topological quantization. Here we report Hall effect measurements, which establish quantitatively the predicted emergent electrodynamics. This allows to obtain quantitative evidence of the depinning of skyrmions from impurities at ultra-low current densities of only 10^6 A/m^2 and their subsequent motion. The combination of exceptionally small current densities and simple transport measurements offers fundamental insights into the connection between emergent and real electrodynamics of skyrmions in chiral magnets, and promises to be important for applications in the long-term.Comment: 24 pages, supplementary information file include

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Magnons are the elementary excitations of a magnetically ordered system. In ferromagnets, only a single band of low-energy magnons needs to be considered, but in ferrimagnets the situation is more complex owing to different magnetic sublattices involved. In this case, low lying optical modes exist that can affect the dynamical response. Here we show that the spin Seebeck effect (SSE) is sensitive to the complexities of the magnon spectrum. The SSE is caused by thermally excited spin dynamics that are converted to a voltage by the inverse spin Hall effect at the interface to a heavy metal contact. By investigating the temperature dependence of the SSE in the ferrimagnet gadolinium iron garnet, with a magnetic compensation point near room temperature, we demonstrate that higher-energy exchange magnons play a key role in the SSE.

Background High gestational weight gain (GWG) has been found to be associated with a number of adverse perinatal and long-term outcomes.Objectives We aimed to perform a systematic review and metaanalysis to find out whether physical activity in pregnancy might help avoid high GWG.Search strategy A literature search in relevant databases and an additional search by hand through bibliographies of various publications were performed.Selection criteria We included randomised controlled trials on healthy women, with increased physical activity as the only intervention. GWG had to be documented for the intervention and control group separately.Data collection and analysis Two reviewers independently extracted data and performed quality assessment. Data from the included trials were combined using a random-effects model. The effect size was expressed as mean difference (MD).Main results Of 1380 studies identified, 12 trials met the inclusion criteria. In seven trials, GWG was lower in the exercise group compared with the control group, whereas five trials showed a lower GWG in the control groups. The meta-analysis resulted in an MD of GWG of )0.61 (95% CI: )1.17, )0.06), suggesting less GWG in the intervention groups compared with the control groups. We found no indication for publication bias or dose effects.Author's conclusions In summary, our analyses suggest that physical activity during pregnancy might be successful in restricting GWG.

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We report on current-induced domain wall motion (CIDWM) in Ta\Co

The aim of the present study was to examine the effects of 8 weeks of exercise training on the fatty acid composition of phospholipids (PL) and triacylglycerols (TG) in rat liver, skeletal muscle (gastrocnemius medialis), and adipose tissue (epididymal and subcutaneous fat). For this purpose, the relevant tissues of 11 trained rats were compared to those of 14 untrained ones. Training caused several significant differences of large effect size in the concentrations and percentages of individual fatty acids in the aforementioned lipid classes. The fatty acid composition of liver PL, in terms of both concentrations and percentages, changed with training. The TG content of muscle and subcutaneous adipose tissue decreased significantly with training. In contrast to the liver, where no significant differences in the fatty acid profile of TG were found, muscle underwent more significant differences in TG than PL, and adipose tissue only in TG. Most differences were in the same direction in muscle and adipose tissue TG, suggesting a common underlying mechanism. Estimated fatty acid elongase activity was significantly higher, whereas Delta(9)-desaturase activity was significantly lower in muscle and adipose tissue of the trained rats. In conclusion, exercise training modified the fatty acid composition of liver PL, muscle PL and TG, as well as adipose tissue TG. These findings may aid in delineating the effects of exercise on biological functions such as membrane properties, cell signaling, and gene expression.

We demonstrate magnetization switching in out-of-plane magnetized Ta\CoFeB\MgO nanowires by current pulse injection along the nanowires, both with and without a constant and uniform magnetic field collinear to the current direction. We deduce that an effective torque arising from spin-orbit effects in the multilayer drives the switching mechanism. While the generation of a component of the magnetization along the current direction is crucial for the switching to occur, we observe that even without a longitudinal field thermally generated magnetization fluctuations can lead to switching. Analysis using a generalized Néel-Brown model enables key parameters of the thermally induced spin-orbit torques switching process to be estimated, such as the attempt frequency and the effective energy barrier.2 Nowadays a large effort is focused on the investigation of novel magnetic materials systems in order to find good candidates for new logic circuits and memory devices. A continuous and growing interest in spin-orbit torque (SOT)-driven magnetization dynamics results from the possibility of using this torque in novel spintronic devices based on ultra-fast current-induced domain wall motion 1 or fast current-induced magnetization switching 2 . The origin of these torques in perpendicularly magnetized multilayers with structural inversion asymmetry (SIA) such as Pt\Co\AlOx 3-6 or Ta\CoFe\MgO 7 seems to be spin-orbit effects generated when an electric current is injected through them. One of the two main effects proposed is the Rashba effect 4,5,8,9 , which generates an in-plane effective magnetic field perpendicular to both the current-flow and the out-ofplane axis. The second one is the spin Hall effect (SHE) 7,[10][11][12][13] , which generates a pure spin-current diffusing across the heavy metal-ferromagnet interface. Such a spin-current has an in-plane spin polarization, which is able to exert a torque on the magnetic texture present in the ferromagnetic layer. However, the debate about the actual origin of the torques is still open. Systems made of Ta\CoFeB\MgO are of particular interest as such a trilayer is already used as a bottom electrode in existing spintronic devices based on CoFeB\MgO\CoFeB magnetic tunnel junctions (MTJs) 14 . The main issue with such devices is the possible damage of the MTJ due to the injection of current across the tunnel barrier, in order to obtain spin-transfer torque (STT)-driven magnetization switching 15 . However, this risk could be mitigated using a three terminal device where switching is driven by SOTs produced by current flowing in plane 16 . In this case only a small read-out current would flow through the tunnel junction -reducing the risk of structural damage to the insulating barrier from high voltages and currents, and making it possible to scale down the cross-section of the MTJs.While the switching of structures using SOTs has been investigated previously 6,7,10 , the switching was only achieved when an additional longitudinal magnetic field was applied, which is cumbersome ...