However, the size and direction of the current induced effective field seems to vary depending on the system and the underlying mechanism of such field generation is not well understood. For example, the effective field in Pt|Co|AlOx is reported to be ~3000 to ~10000 Oe for a current density of 10 8 A/cm 2 , pointing perpendicular to both the film normal and the current flow direction (defined as a transverse field hereafter) 4,13 . More recently, in the same system, signs of current induced effective field directed along the current flow, i.e. Here we show a systematic study of the current induced effective field in Ta|CoFeB|MgO.We use a low current excitation technique to quantitatively evaluate the size and direction of the effective field. We find that the size and even the sign of the transverse and longitudinal effective fields vary as the Ta layer thickness is changed, suggesting competing contributions from two distinct sources. We find that the transverse effective field is larger than the longitudinal field, by nearly a factor of three, when the Ta layer thickness is large. In contrast, the relative size of the two components shows somewhat an oscillatory dependence on the Ta thickness for films with thin Ta.Films are sputtered on a highly resistive silicon substrate coated with 100 nm thick thermally oxidized SiO 2 . We use a linear shutter during the sputtering to vary the thickness of one layer in each substrate. Two film stacks are prepared here: Ta wedge: Si-sub|d Ta Ta|1 Co 20 We set the thickness of each layer, d Ta and t CoFeB , to vary from ~0 to ~2 nm. Throughout this paper, the nominal thickness is used for the Ta wedge. For the CoFeB wedge film, correction of the thickness was required due to technical reasons, and thus we use our resistivity results to calibrate the thickness. All films are annealed at 300 °C for one hour ex-situ after the film deposition. Photo-lithography and Ar ion etching are used to pattern Hall bars from the film and a lift off process is used to form the contact electrodes (10 Ta|100 Au). Prior to the deposition of the contact electrodes, we etch the Ta capping layer and nearly half of the MgO layer to avoid large contact resistance. Although etching of the MgO layer significantly influences the magnetic anisotropy of the CoFeB layer under the etched region 24 , here we assume that this has little effect on the evaluation of the current induced effective fields since we limit the applied field smaller than the magnetization switching field. 4Schematic illustration of the experimental set up and definition of the coordinate system are shown in Fig 1(a). The width and length of typical wires measured are 10 m and 60 m, respectively. We measure wires with different width, ranging from 5 m to 30 m, and find little dependence on the width for most of the parameters shown here. Positive current is defined as current flowing along the +y direction in Fig 1(a). Current is fed into the wire and the Hall voltage is measured in all experiments. Using the Extraordinary Hal...

The spin transfer torque is essential for electrical magnetization switching. When a magnetic domain wall is driven by an electric current through an adiabatic spin torque, the theory predicts a threshold current even for a perfect wire without any extrinsic pinning. The experimental confirmation of this 'intrinsic pinning', however, has long been missing. Here, we give evidence that this intrinsic pinning determines the threshold, and thus that the adiabatic spin torque dominates the domain wall motion in a perpendicularly magnetized Co/Ni nanowire. The intrinsic nature manifests itself both in the field-independent threshold current and in the presence of its minimum on tuning the wire width. The demonstrated domain wall motion purely due to the adiabatic spin torque will serve to achieve robust operation and low energy consumption in spintronic devices.

We report on the local atomic and electronic structures of a nitrogen-doped graphite surface by scanning tunneling microscopy, scanning tunneling spectroscopy, x-ray photoelectron spectroscopy, and first-principles calculations. The nitrogen-doped graphite was prepared by nitrogen ion bombardment followed by thermal annealing. Two types of nitrogen species were identified at the atomic level: pyridinic-N (N bonded to two C nearest neighbors) and graphitic-N (N bonded to three C nearest neighbors). Distinct electronic states of localized π states were found to appear in the occupied and unoccupied regions near the Fermi level at the carbon atoms around pyridinic-N and graphitic-N species, respectively. The origin of these states is discussed based on experimental results and theoretical simulations.

Multiple severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants with higher transmission potential have been emerging globally, including SARS-CoV-2 variants from the United Kingdom and South Africa. We report 4 travelers from Brazil to Japan in January 2021 infected with a novel SARS-CoV-2 variant with an additional set of mutations.

Interpretation: Although the number of patients is limited, our results show that the antibody response against the first SARS-CoV-2 infection in symptomatic patients is typical of that observed in an acute viral infection.