We study the device size dependence of spin-orbit torque induced magnetization switching in a Ta/CoFeB/MgO structure with perpendicular easy axis. The miniaturization of the device from micrometer-sized wire to 80-nm dot results in the increase of the threshold current density Jth by one order, whereas Jth increases only slightly with further reducing the device size down to 30 nm. No significant increase in Jth is seen, as the current pulse width decreases from 100 ms down to 3 ns. We reveal that the switching in devices at reduced size is reasonably well explained by the macrospin model, in which the effects of both the Slonczewski-like torque and field-like torque are included.

No abstract

A Ni-Cr nanocomposite with an average Cr concentration of 11 ͑wt %͒ was deposited onto nickel plate by simultaneous electrodeposition of Ni and Cr nanoparticles from a nickel sulfate bath. The nanocomposite consisted of a nanocrystalline Ni matrix and dispersed Cr nanoparticles with a mean size of 33 nm. For comparison, two Ni-Cr alloys, one with similar Cr content ͑10 wt %͒ and the other with much higher Cr content ͑20 wt %͒, were prepared using electro-arc melting. Hot corrosion testing under molten Na 2 SO 4 -K 2 SO 4 -NaCl in air at 700°C showed that rapid formation of a continuous chromia-rich scale is essential for hot corrosion protection. This was the case only for the nanocomposite. Internal sulfidation was observed for arc-melted alloys, but not for the nanocomposite. The results demonstrate that it was not primarily the Cr content but the unique structure of the nanocomposite that was responsible for its superior hot corrosion resistance. The protection mechanism lies in the fast formation of a continuous chromia scale on the nanocomposite, due to the easy nucleation of chromia on both chromium nanoparticles and abundant nickel grain boundaries, and then fast linking of the nuclei as a result of enhanced diffusion of Cr through those grain boundaries.

No abstract

No abstract

No abstract

No abstract

The surface of the olfactory epithelium of two species of cave loaches in China, Oreonectes polystigmus and O. guananensis, was studied by scanning electron microscopy (SEM). The structure of the olfactory organ of the two species is quite different from each other; as well, the distribution patterns of cell types in the olfactory epithelium of the studied species showed interesting features. A needle-like spine is visible on the lamellae of the olfactory organ of O. polystigmus, which is a unique character in this species. Ciliated non-sensory cells and microvillus sensory cells showed a different distribution in the two species, being more numerous in O. polystigmus. The non-sensory elements in O. guananensis were ciliated non-sensory cells, with microridges and chloride cells. The presence of chloride cells in the olfactory epithelium of O. guananensis may be of special interest in this species; otherwise, possible differences and physiological changes of the concerned species should be taken into account in order to explain such variability in cell types