Controlled skyrmion nucleation in extended magnetic layers using a nanocontact geometry

We propose and numerically simulate a spintronic device layout consisting of a nanocontact on top of an extended Co/Pt bilayer. The interfacial Dzyaloshinskii-Moriya interaction in such bilayer systems can lead to the possible existence of metastable skyrmions. A small dc current injected through the nanocontact enables the manipulation of the size as well as the annihilation of an initially present skyrmion, while ps-long current pulses allow for the controlled nucleation of single skyrmions underneath the nanocontact. The results are obtained from micromagnetic simulations and can be potentially used for future magnetic storage implementations

Hybrid spintronic materials:Growth, structure and properties

10.1016/j.pmatsci.2018.08.001Progress in Materials Science9927-10

Planar carbon nanotube-graphene hybrid films for high-performance broadband photodetectors

Graphene has emerged as a promising material for photonic applications fuelled by its superior electronic and optical properties. However, the photoresponsivity is limited by the low absorption cross section and ultrafast recombination rates of photoexcited carriers. Here we demonstrate a photoconductive gain of $\sim$ 10$^5$ electrons per photon in a carbon nanotube-graphene one dimensional-two dimensional hybrid due to efficient photocarriers generation and transport within the nanostructure. A broadband photodetector (covering 400 nm to 1550 nm) based on such hybrid films is fabricated with a high photoresponsivity of more than 100 AW$^{-1}$ and a fast response time of approximately 100 {\mu}s. The combination of ultra-broad bandwidth, high responsivities and fast operating speeds affords new opportunities for facile and scalable fabrication of all-carbon optoelectronic devices.Comment: 21 pages, 3 figure

Mir-23b down-regulates the expression of target gene of acetaldehyde dehydrogenase 1a1 and increases the sensitivity of cervical cancer stem cells to cisplatin

Purpose: To study the effect of miR-23b on the expression of the target gene of acetaldehyde dehydrogenase 1A1 (ALDH1A1), and cisplatin (CDDP) susceptibility of cervical carcinoma stem cells. Methods: Human cervical cancer cell line Hela cells were cultured in vitro, and miR-23b mimic and negative control were transfected into the cells using lipofectamine method. The growth of the two groups of cells was determined using growth curve method, and their proliferation measured using plate clone formation. The influence of treatments on the sensitivity of the cells to CDDP was assayed using MTT method. The mRNA expression of ALDH1A1 in Hela cells was assayed using real-time quantitative polymerase hain reation (PCR), while its protein expression was assayed by Western blot. Results: The levels of expressions of ALDH1A1 protein and mRNA in the miR-23b overexpression group were significantly lower than those in the control group (p < 0.05). The sensitivities of Hela cells to CDDP in the ALDH1A1 inhibition group and the control group were dose-dependent to some extent, but cell inhibition in ALDH1A1 inhibition group markedly increased, relative to control when the CDDP dose was 0.1 ppc (p < 0.01). Conclusion: Up-regulating the expression of miR-23b significantly inhibits the growth and proliferation of cervical cancer cells, and increases their sensitivity to CDDP via down-regulation of the expression of the target gene for ALDH1A1. Therefore, during cervical carcinoma treatment, increasing the level of miR-23b may produce a chemotherapeutic effect. Keywords: MiR-23b, Acetaldehyde dehydrogenase 1A1, Cervical cancer, Cisplatin, Sensitivit

Directional Spin Wave in Spin-Torque Oscillators Induced by Interfacial Dzyaloshinskii–Moriya Interaction

Spin torque oscillators (STOs) are currently of great interest due to its wide tunable frequencies, low energy consumption and high quality factors compared with traditional oscillators. Here, we report the characteristics of the nanocontact-(NC-)STO in the presence of interfacial Dzyaloshinskii-Moriya interaction (DMI), using micromagnetic simulations. We find that the DMI can decrease the STO frequency by around 2 GHz. More importantly, the DMI is able to break the isotropy of the spin-wave spectrum and turn the emitted microwave into directional spin-wave beams potentially facilitating the synchronization of multiple STOs

Quantum Oscillations from Nontrivial States in Quasi-Two-Dimensional Dirac Semimetal ZrTe 5 Nanowires

Recently discovered Dirac semimetal ZrTe 5 bulk crystal, exhibits nontrivial conducting states in each individual layer, holding great potential for novel spintronic applications. Here, to reveal the transport properties of ZrTe 5 , we fabricated ZrTe 5 nanowires (NWs) devices, with much larger surface-to-volume ratio than bulk materials. Quantum oscillations induced by the two-dimensional (2D) nontrivial conducting states have been observed from these NWs and a finite Berry phase of ~π is obtained by the analysis of Landau-level fan diagram. More importantly, the absence of the Aharonov-Bohm (A-B) oscillations, along with the SdH oscillations, suggests that the electrons only conduct inside each layer. And the intralayer conducting is suppressed because of the weak connection between adjacent layers. Our results demonstrate that ZrTe 5 NWs can serve as a suitable quasi-2D Dirac semimetal with high mobility (~85000 cm 2 V −1 s −1 ) and large nontrivial conductance contribution (up to 8.68%)

Experimental Observation of Dual Magnetic States in Topological Insulators

The recently discovered topological phase offers new possibilities for spintronics and condensed matter. Even insulating material exhibits conductivity at the edges of certain systems, giving rise to an anomalous quantum Hall effect and other coherent spin transport phenomena, in which heat dissipation is minimized, with potential uses for next-generation energy-efficient electronics. While the metallic surface states of topological insulators (TIs) have been extensively studied, direct comparison of the surface and bulk magnetic properties of TIs has been little explored. We report unambiguous evidence for distinctly enhanced surface magnetism in a prototype magnetic TI, Cr-doped Bi 2 Se 3 . Using synchrotron-based x-ray techniques, we demonstrate a “three-step transition” model, with a temperature window of ~15 K, where the TI surface is magnetically ordered while the bulk is not. Understanding the dual magnetization process has strong implications for defining a physical model of magnetic TIs and lays the foundation for applications to information technology