Influence of CoFeB layer thickness on elastic parameters in CoFeB/MgO heterostructures.

The surface acoustic waves, i.e., surface phonons may have huge potential for future spintronic devices, if coupled to other waves (e.g., spin waves) or quasiparticles. In order to understand the coupling of acoustic phonons with the spin degree of freedom, especially in magnetic thin film-based heterostructures, one needs to investigate the properties of phonons in those heterostructures. This also allows us to determine the elastic properties of individual magnetic layers and the effective elastic parameters of the whole stacks. Here, we study frequency versus wavevector dispersion of thermally excited SAWs in CoFeB/MgO heterostructures with varying CoFeB thickness by employing Brillouin light spectroscopy. The experimental results are corroborated by finite element method-based simulations. From the best agreement of simulation results with the experiments, we find out the elastic tensor parameters for CoFeB layer. Additionally, we estimate the effective elastic parameters (elastic tensors, Young's modulus, Poisson's ratio) of the whole stacks for varying CoFeB thickness. Interestingly, the simulation results, either considering elastic parameters of individual layers or considering effective elastic parameters of whole stacks, show good agreement with the experimental results. These extracted elastic parameters will be very useful to understand the interaction of phonons with other quasiparticles.

The 2021 Magnonics Roadmap.

Magnonics is a budding research field in nanomagnetism and nanoscience that addresses the use of spin waves (magnons) to transmit, store, and process information. The rapid advancements of this field during last one decade in terms of upsurge in research papers, review articles, citations, proposals of devices as well as introduction of new sub-topics prompted us to present the first roadmap on magnonics. This is a collection of 22 sections written by leading experts in this field who review and discuss the current status besides presenting their vision of future perspectives. Today, the principal challenges in applied magnonics are the excitation of sub-100 nm wavelength magnons, their manipulation on the nanoscale and the creation of sub-micrometre devices using low-Gilbert damping magnetic materials and its interconnections to standard electronics. To this end, magnonics offers lower energy consumption, easier integrability and compatibility with CMOS structure, reprogrammability, shorter wavelength, smaller device features, anisotropic properties, negative group velocity, non-reciprocity and efficient tunability by various external stimuli to name a few. Hence, despite being a young research field, magnonics has come a long way since its early inception. This roadmap asserts a milestone for future emerging research directions in magnonics, and hopefully, it will inspire a series of exciting new articles on the same topic in the coming years.

Propagation dynamics of spin excitations along skyrmion strings.

Magnetic skyrmions, topological solitons characterized by a two-dimensional swirling spin texture, have recently attracted attention as stable particle-like objects. In a three-dimensional system, a skyrmion can extend in the third dimension forming a robust and flexible string structure, whose unique topology and symmetry are anticipated to host nontrivial functional responses. Here we experimentally demonstrate the coherent propagation of spin excitations along skyrmion strings for the chiral-lattice magnet Cu2OSeO3. We find that this propagation is directionally non-reciprocal and the degree of non-reciprocity, as well as group velocity and decay length, are strongly dependent on the character of the excitation modes. These spin excitations can propagate over a distance exceeding 50 µm, demonstrating the excellent long-range ordered nature of the skyrmion-string structure. Our combined experimental and theoretical analyses offer a comprehensive account of the propagation dynamics of skyrmion-string excitations and suggest the possibility of unidirectional information transfer along such topologically protected strings.

Realization of Spin-dependent Functionality by Covering a Metal Surface with a Single Layer of Molecules.

An interface of molecule and metal has attracted much attention in the research field of nanoelectronics because of their high degree of design freedom. Here, we demonstrate an efficient spin-to-charge current conversion at the metal surface covered by a single layer of molecules. Spin currents are injected into an interface between metal (Cu) and lead(II) phthalocyanine by means of the spin pumping method. An observed voltage signal is caused by the inverse Edelstein effect, i.e., spin-to-charge current conversion at the interface. The conversion coefficient, inverse Edelstein length, is estimated to be 0.40 ± 0.06 nm, comparable with the largest Rashba spin splitting of interfaces with heavy metals. Interestingly, the Edelstein length strongly depends on the thickness of the molecule and takes a maximum value when a single layer of molecules is formed on the Cu surface. Comparative analysis between scanning probe microscopy and first-principles calculations reveal that the formation of interface state with Rashba spin splitting causes the inverse Edelstein effect, whose magnitude is sensitive to the adsorption configuration of the molecules.

Nosocomial Mycobacterium tuberculosis transmission by brief casual contact identified using comparative genomics.

This paper reports a case of nosocomial transmission of Mycobacterium tuberculosis by brief casual contact. Routine variable number tandem repeat typing in Yamagata Prefecture, Japan found that M. tuberculosis clinical isolates from two patients showed indistinguishable genotypes. The patients had an epidemiological relationship of sharing a waiting room in a hospital on the same day. As comparative genomics detected only two single nucleotide variants between the isolates, it was concluded that recent tuberculosis transmission occurred in the waiting room. These results indicate that the physical separation of infectious tuberculosis patients is an essential control measure for preventing unpredictable nosocomial transmission by casual contact.

Fibroblast growth factor 13 regulates glioma cell invasion and is important for bevacizumab-induced glioma invasion.

Glioblastoma has the poorest prognosis, and is characterized by excessive invasion and angiogenesis. To determine the invasive mechanisms, we previously used two glioma cell lines (J3T-1 and J3T-2) with different invasive phenotypes. The J3T-1 showed abundant angiogenesis and tumor cell invasion around neovasculature, while J3T-2 showed diffuse cell infiltration into surrounding healthy parenchyma. Microarray analyses were used to identify invasion-related genes in J3T-2 cells, and the expressed genes and their intracellular and intratumoral distribution patterns were evaluated in J3T-2 cell lines, human glioma cell lines, human glioblastoma stem cells and human glioblastoma specimens. To determine the role of the invasion-related genes, invasive activities were evaluated in vitro and in vivo. Fibroblast growth factor 13 (FGF13) was overexpressed in J3T-2 cells compared to J3T-1 cells, and in human glioma cell lines, human glioblastoma stem cells and human glioblastoma specimens, when compared to that of normal human astrocytes. Immunohistochemical staining and the RNA-seq (sequencing) data from the IVY Glioblastoma Atlas Project showed FGF13 expression in glioma cells in the invasive edges of tumor specimens. Also, the intracellular distribution was mainly in the cytoplasm of tumor cells and colocalized with tubulin. Overexpression of FGF13 stabilized tubulin dynamics in vitro and knockdown of FGF13 decreased glioma invasion both in vitro and in vivo and prolonged overall survival of several xenograft models. FGF13 was negatively regulated by hypoxic condition. Silencing of FGF13 also decreased in vivo bevacizumab-induced glioma invasion. In conclusion, FGF13 regulated glioma cell invasion and bevacizumab-induced glioma invasion, and could be a novel target for glioma treatment.

Current-Nonlinear Hall Effect and Spin-Orbit Torque Magnetization Switching in a Magnetic Topological Insulator.

The current-nonlinear Hall effect or second harmonic Hall voltage is widely used as one of the methods for estimating charge-spin conversion efficiency, which is attributed to the magnetization oscillation by spin-orbit torque (SOT). Here, we argue the second harmonic Hall voltage under a large in-plane magnetic field with an in-plane magnetization configuration in magnetic-nonmagnetic topological insulator (TI) heterostructures, Cr_{x}(Bi_{1-y}Sb_{y})_{2-x}Te_{3}/(Bi_{1-y}Sb_{y})_{2}Te_{3}, where it is clearly shown that the large second harmonic voltage is governed not by SOT but mainly by asymmetric magnon scattering without macroscopic magnetization oscillation. Thus, this method does not allow an accurate estimation of charge-spin conversion efficiency in TI. Instead, the SOT contribution is exemplified by current pulse induced nonvolatile magnetization switching, which is realized with a current density of 2.5×10^{10} A m^{-2}, showing its potential as a spintronic material.

Development of beam emission spectroscopy for turbulence transport study in Heliotron J.

This paper describes the development study of the beam emission spectroscopy (BES) for the turbulent transport study in Heliotron J. Modification of the sightlines (10 × 4 for edge and 10 × 2 for edge) enables us to obtain 2-dimensional BES imaging. The cooling effect on the reduction in the electrical noise of avalanche photodiode (APD) assembly has been investigated using a refrigerant cooling system. When the temperature of the APD element has set to be -20 °C, the electrical noise can be reduced more than 50%. The measurement error of the phase difference in the case of low signal level has been tested by two light-emitting diode lamps. The APD cooling has an effect to improve the measurement error at the low signal level of APD.

Strong Suppression of the Spin Hall Effect in the Spin Glass State.

We have measured spin Hall effects in spin glass metals, CuMnBi alloys, with the spin absorption method in the lateral spin valve structure. Far above the spin glass temperature T(g) where the magnetic moments of Mn impurities are randomly frozen, the spin Hall angle of a CuMnBi ternary alloy is as large as that of a CuBi binary alloy. Surprisingly, however, it starts to decrease at about 4T(g) and becomes as little as 7 times smaller at 0.5T(g). A similar tendency was also observed in anomalous Hall effects in the ternary alloys. We propose an explanation in terms of a simple model considering the relative dynamics between the localized moment and the conduction electron spin.

Quasiparticle-mediated spin Hall effect in a superconductor.

In some materials the competition between superconductivity and magnetism brings about a variety of unique phenomena such as the coexistence of superconductivity and magnetism in heavy-fermion superconductors or spin-triplet supercurrent in ferromagnetic Josephson junctions. Recent observations of spin-charge separation in a lateral spin valve with a superconductor evidence that these remarkable properties are applicable to spintronics, although there are still few works exploring this possibility. Here, we report the experimental observation of the quasiparticle-mediated spin Hall effect in a superconductor, NbN. This compound exhibits the inverse spin Hall (ISH) effect even below the superconducting transition temperature. Surprisingly, the ISH signal increases by more than 2,000 times compared with that in the normal state with a decrease of the injected spin current. The effect disappears when the distance between the voltage probes becomes larger than the charge imbalance length, corroborating that the huge ISH signals measured are mediated by quasiparticles.

Realization of a micrometre-scale spin-wave interferometer.

The recent development of spin dynamics opens perspectives for various applications based on spin waves, including logic devices. The first important step in the realization of spin-wave-based logics is the manipulation of spin-wave interference. Here, we present the experimental realization of a micrometre-scale spin-wave interferometer consisting of two parallel spin-wave waveguides. The spin waves propagate through the waveguides and the superposition or interference of the electrical signals corresponding to the spin waves is measured. A direct current flowing through a metal wire underneath one of the spin-wave waveguides affects the propagation properties of the corresponding spin wave. The signal of constructive or destructive interference depends on the magnitude and direction of the applied direct current. Thus, the present work demonstrates a unique manipulation of spin-wave interference.

Development of a high-volume air sampler for nanoparticles.

As a tool to evaluate the characteristics of aerosol nano-particles, a high-volume air sampler for the collection of nano-particles was developed based on the inertial filter technology. Instead of the webbed fiber geometry of the existing inertial filter, wire mesh screens alternately layered using spacing sheets with circular holes aligned to provide multi-circular nozzles were newly devised and the separation performance of the filter was investigated experimentally. The separation performance was evaluated for a single-nozzle inertial filter at different filtration velocities. A webbed stainless steel fiber mat attached on the inlet surface of the developed inertial filter was discussed as a pre-separator suppressing the bouncing of particles on meshes. The separation performance of a triple-nozzle inertial filter was also discussed to investigate the influence of scale-up on the separation performance of a multi-nozzle inertial filter. The influence of particle loading on the pressure drop and separation performance was discussed. A supplemental inlet for the nano-particle collection applied to an existing portable high-volume air sampler was devised and the consistency with other types of existing samplers was discussed based on the sampling of ambient particles. The layered-mesh inertial filter with a webbed stainless steel fiber mat as a pre-separator showed good performance in the separation of particles with a d p50 ranging from 150 to 190 nm keeping the influence of loaded particles small. The developed layered-mesh inertial filter was successfully applied to the collection of particles at a d p50∼ 190 nm that was consistent with the results from existing samplers.

Giant spin Hall effect induced by skew scattering from bismuth impurities inside thin film CuBi alloys.

We demonstrate that a giant spin Hall effect (SHE) can be induced by introducing a small amount of Bi impurities in Cu. Our analysis, based on a new three-dimensional finite element treatment of spin transport, shows that the sign of the SHE induced by the Bi impurities is negative and its spin Hall (SH) angle amounts to -0.24. Such a negative large SH angle in CuBi alloys can be explained by applying the resonant scattering model proposed by Fert and Levy [Phys. Rev. Lett. 106, 157208 (2011)] to 6p impurities.

The spin Hall effect as a probe of nonlinear spin fluctuations.

The spin Hall effect and its inverse have key roles in spintronic devices as they allow conversion of charge currents to and from spin currents. The conversion efficiency strongly depends on material details, such as the electronic band structure and the nature of impurities. Here we show an anomaly in the inverse spin Hall effect in weak ferromagnetic NiPd alloys near their Curie temperatures with a shape independent of material details, such as Ni concentrations. By extending Kondo's model for the anomalous Hall effect, we explain the observed anomaly as originating from the second-order nonlinear spin fluctuation of Ni moments. This brings to light an essential symmetry difference between the spin Hall effect and the anomalous Hall effect, which reflects the first-order nonlinear fluctuations of local moments. Our finding opens up a new application of the spin Hall effect, by which a minuscule magnetic moment can be detected.

Optical detection of spin transport in nonmagnetic metals.

We determine the dynamic magnetization induced in nonmagnetic metal wedges composed of silver, copper, and platinum by means of Brillouin light scattering microscopy. The magnetization is transferred from a ferromagnetic Ni80Fe20 layer to the metal wedge via the spin pumping effect. The spin pumping efficiency can be controlled by adding an insulating interlayer between the magnetic and nonmagnetic layer. By comparing the experimental results to a dynamical macroscopic spin-transport model we determine the transverse relaxation time of the pumped spin current which is much smaller than the longitudinal relaxation time.

Extrinsic spin Hall effect induced by iridium impurities in copper.

We study the extrinsic spin Hall effect induced by Ir impurities in Cu by injecting a pure spin current into a CuIr wire from a lateral spin valve structure. While no spin Hall effect is observed without Ir impurity, the spin Hall resistivity of CuIr increases linearly with the impurity concentration. The spin Hall angle of CuIr, (2.1±0.6)% throughout the concentration range between 1% and 12%, is practically independent of temperature. These results represent a clear example of predominant skew scattering extrinsic contribution to the spin Hall effect in a nonmagnetic alloy.

The clinical significance of serum procalcitonin levels following direct hemoperfusion with polymyxin B-immobilized fiber column in septic patients with colorectal perforation.

BACKGROUND: The efficacy of direct hemoperfusion with polymyxin B-immobilized fiber columns (PMX) has already been demonstrated in clinical studies for the treatment of septic shock. However, serum procalcitonin levels following PMX remain unknown. METHODS: This prospective, multicenter, nonrandomized clinical study was performed at 12 institutions. Forty-five patients with severe sepsis or septic shock due to colorectal perforation underwent PMX. Patients' outcome as well as circulating levels of endotoxin, procalcitonin and IL-6 were monitored. RESULTS: Before surgery, procalcitonin level, but not endotoxin and IL-6 levels, was elevated according to patients' septic conditions. Procalcitonin was significantly and positively correlated with sequential organ failure assessment score. Circulating levels of procalcitonin peaked 24 h after PMX treatment. Change in serum procalcitonin level was significantly higher in nonsurvivors than survivors. Nine mortalities were observed within 28 days. The best predictor for 28-day mortality was procalcitonin >85.7 ng/ml at 24 h after PMX (area under the receiver operating characteristic curve: 0.808 +/- 0.105). CONCLUSIONS: Procalcitonin may be a good indicator of severity of sepsis secondary to colorectal perforation. Furthermore, procalcitonin level at 24 h after PMX appears to predict outcome after PMX. Therefore, procalcitonin may be a useful diagnostic marker to evaluate patients' condition in candidates for PMX treatment.

Changes in hepatic key enzymes of dairy calves in early weaning production systems.

The objective of the present study was to describe plasma hormonal and metabolite profile and mRNA expression levels and activities of the enzymes pyruvate carboxylase (PC), phosphoenolpyruvate carboxykinase (PEPCK), and acetyl-coenzyme A (CoA) carboxylase in the liver of male Holstein calves before (1 and 3 wk of age) and after (8, 13, and 19 wk of age) weaning at 6 wk of age. The mean plasma concentration of acetate and beta-hydroxybutyrate increased, and that of plasma lactate and nonesterified fatty acids decreased with week, particularly after weaning. Plasma glucose concentration was lowest at 8 wk of age. The mean plasma concentration of insulin and glucagon did not change with time, and that of cortisol was greatest at 1 wk of age. In the liver, enzyme activity of PC was greatest at 1 wk of age and decreased with time. There was a significant relationship between the activity and the mRNA level for PC. Activity of PEPCK also decreased with week. Acetyl-CoA carboxylase activity tended to decrease with week, and activity at 13 wk of age was lower than that at other times. Expression of PC mRNA, but not that of PEPCK and acetyl-CoA carboxylase alpha, decreased with week. We conclude that the hepatic gluconeogenic enzymes and acetyl-CoA carboxylase activities tend to decrease with age, reflecting changes in plasma metabolites in early weaning production systems.