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We investigate the surface oxidation in a van der Waals ferromagnet Fe3-xGeTe2, a material widely utilized for spintronic applications. While known for its relative air-insensitivity, exposure to air during the handling process (e.g. device or heterostructure fabrication) can lead to reduction or disappearance of its magnetic signal. Comparison of x-ray absorption and x-ray magnetic circular dichroism spectra between pristine and air-exposed Fe3-xGeTe2 confirm a naturally oxidized surface layer on the material. The surface oxide layer has predominantly Fe3+ content. X-ray absorption spectroscopy done on micron-sized exfoliated Fe3-xGeTe2 flakes reveal that the change in the surface chemical properties can be quite significant for thin flakes. The surface modulation of Fe3-xGeTe2 can lead to inaccuracies in characterizing its interfacial magnetic and spin transport properties, and complicate device and heterostructure fabrication processes.

Background Skeletal muscle as a metabolic consumer determines systemic energy homeostasis by regulating myofibre type conversion and muscle mass control. Perturbation of the skeletal muscle metabolism elevates the risk of a variety of diseases including metabolic disorders. However, the regulatory pathways and molecules are not completely understood. The discovery of relevant responsible molecules and the associated network could be an attractive strategy to overcome diseases associated with muscle problems. Methods An initial screening using quantitative trait locus analysis enabled us to extract a set of genes including ubiquitin‐specific proteases21 (USP21) (r = 0.738; P = 0.004) as potential targets associated with fasting blood glucose content. Given tight regulation of the ubiquitination status of proteins in muscle, we focused on USP21 and generated whole‐body (KO) and skeletal muscle‐specific USP21 knockout (MKO) mice. Transcriptomics, proteomics, and lipidomics assays in combination with various in vivo and in vitro experiments were performed to understand the functions of USP21 and underlying mechanisms. A high‐fat diet (60%)‐fed mouse model and diabetic patient‐derived samples were utilized to assess the effects of USP21 on energy metabolism in skeletal muscle. Results USP21 was highly expressed in both human and mouse skeletal muscle, and controlled skeletal muscle oxidative capacity and fuel consumption. USP21‐KO or USP21‐MKO significantly promoted oxidative fibre type changes (Δ36.6% or Δ47.2%), muscle mass increase (Δ13.8% to Δ22.8%), and energy expenditure through mitochondrial biogenesis, fatty acid oxidation, and UCP2/3 induction (P

Identifying material parameters affecting properties of ferromagnets is key to optimized materials that are better suited for spintronics. Magnetic anisotropy is of particular importance in van der Waals magnets, since it not only influences magnetic and spin transport properties, but also is essential to stabilizing magnetic order in the two-dimensional limit. Here, we report that hole doping effectively modulates the magnetic anisotropy of a van der Waals ferromagnet and explore the physical origin of this effect. Fe3-xGeTe2 nanoflakes show a significant suppression of the magnetic anisotropy with hole doping. Electronic structure measurements and calculations reveal that the chemical potential shift associated with hole doping is responsible for the reduced magnetic anisotropy by decreasing the energy gain from the spin-orbit induced band splitting. Our findings provide an understanding of the intricate connection between electronic structures and magnetic properties in two-dimensional magnets and propose a method to engineer magnetic properties through doping.

Thickness-dependent magnetic domain structure of ultrathin Co wedge films (0.3 nm–1.0 nm) sandwiched by Pt layers was investigated by scanning transmission x-ray microscopy (STXM) employing X-ray magnetic circular dichroism (XMCD), utilizing elliptically polarized soft x-rays and electromagnetic fields, with a spatial resolution of 50 nm. The magnetic domain images measured at the Co L3 edge showed the evolution of the magnetic domain structures from maze-like form to the bubble-like form as the perpendicular magnetic field was applied. The asymmetric domain expansion of a 500 nm-scale bubble domain was also measured when the in-plane and perpendicular external magnetic field were applied simultaneously.

The pathogenesis of psoriasis, an immune-mediated chronic skin barrier disease, is not fully understood yet. Here, we identified lysophosphatidic acid (LPA) receptor 5 (LPA5)-mediated signaling as a novel pathogenic factor in psoriasis using an imiquimod-induced psoriasis mouse model. Amounts of most LPA species were markedly elevated in injured skin of psoriasis mice, along with LPA5 upregulation in injured skin. Suppressing the activity of LPA5 with TCLPA5, a selective LPA5 antagonist, improved psoriasis symptoms, including ear thickening, skin erythema, and skin scaling in imiquimod-challenged mice. TCLPA5 administration attenuated dermal infiltration of macrophages that were found as the major cell type for LPA5 upregulation in psoriasis lesions. Notably, TCLPA5 administration attenuated the upregulation of macrophage NLRP3 in injured skin of mice with imiquimod-induced psoriasis. This critical role of LPA5 in macrophage NLRP3 was further addressed using lipopolysaccharide-primed bone marrow-derived macrophages. LPA exposure activated NLRP3 inflammasome in lipopolysaccharide-primed cells, which was evidenced by NLRP3 upregulation, caspase-1 activation, and IL-1&beta, maturation/secretion. This LPA-driven NLRP3 inflammasome activation in lipopolysaccharide-primed cells was significantly attenuated upon LPA5 knockdown. Overall, our findings establish a pathogenic role of LPA5 in psoriasis along with an underlying mechanism, further suggesting LPA5 antagonism as a potential strategy to treat psoriasis.

Fibroblast growth factor 23 (FGF23) is a bone-derived hormone that controls blood phosphate levels by increasing renal phosphate excretion and reducing 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D] production. Disorders of FGF23 homeostasis are associated with significant morbidity and mortality, but a fundamental understanding of what regulates FGF23 production is lacking. Because the kidney is the major end organ of FGF23 action, we hypothesized that it releases a factor that regulates FGF23 synthesis. Using aptamer-based proteomics and liquid chromatography–mass spectrometry–based (LC-MS–based) metabolomics, we profiled more than 1600 molecules in renal venous plasma obtained from human subjects. Renal vein glycerol-3-phosphate (G-3-P) had the strongest correlation with circulating FGF23. In mice, exogenous G-3-P stimulated bone and bone marrow FGF23 production through local G-3-P acyltransferase–mediated (GPAT-mediated) lysophosphatidic acid (LPA) synthesis. Further, the stimulatory effect of G-3-P and LPA on FGF23 required LPA receptor 1 (LPAR1). Acute kidney injury (AKI), which increases FGF23 levels, rapidly increased circulating G-3-P in humans and mice, and the effect of AKI on FGF23 was abrogated by GPAT inhibition or Lpar1 deletion. Together, our findings establish a role for kidney-derived G-3-P in mineral metabolism and outline potential targets to modulate FGF23 production during kidney injury.

Identifying material parameters affecting properties of ferromagnets is key to optimized materials that are better suited for spintronics. Magnetic anisotropy is of particular importance in van der Waals magnets, since it not only influences magnetic and spin transport properties, but also is essential to stabilizing magnetic order in the two-dimensional limit. Here, we report that hole doping effectively modulates the magnetic anisotropy of a van der Waals ferromagnet and explore the physical origin of this effect. Fe

Two-dimensional (2D)-layered semiconducting materials with considerable band gaps are emerging as a new class of materials applicable to next-generation devices. Particularly, black phosphorus (BP) is considered to be very promising for next-generation 2D electrical and optical devices because of its high carrier mobility of 200–1000 cm2 V–1 s–1 and large on/off ratio of 104 to 105 in field-effect transistors (FETs). However, its environmental instability in air requires fabrication processes in a glovebox filled with nitrogen or argon gas followed by encapsulation, passivation, and chemical functionalization of BP. Here, we report a new method for reduction of BP-channel devices fabricated without the use of a glovebox by galvanic corrosion of an Al overlayer. The reduction of BP induced by an anodic oxidation of Al overlayer is demonstrated through surface characterization of BP using atomic force microscopy, Raman spectroscopy, and X-ray photoemission spectroscopy along with electrical measurement of a...

Summary The reactions catalyzed by the delta-5 and delta-6 desaturases (D5D/D6D), key enzymes responsible for highly unsaturated fatty acid (HUFA) synthesis, regenerate NAD+ from NADH. Here, we show that D5D/D6D provide a mechanism for glycolytic NAD+ recycling that permits ongoing glycolysis and cell viability when the cytosolic NAD+/NADH ratio is reduced, analogous to lactate fermentation. Although lesser in magnitude than lactate production, this desaturase-mediated NAD+ recycling is acutely adaptive when aerobic respiration is impaired in vivo. Notably, inhibition of either HUFA synthesis or lactate fermentation increases the other, underscoring their interdependence. Consistent with this, a type 2 diabetes risk haplotype in SLC16A11 that reduces pyruvate transport (thus limiting lactate production) increases D5D/D6D activity in vitro and in humans, demonstrating a chronic effect of desaturase-mediated NAD+ recycling. These findings highlight key biologic roles for D5D/D6D activity independent of their HUFA end products and expand the current paradigm of glycolytic NAD+ regeneration.

Graphene-based spintronics has attracted much attention owing to the weak spin–orbit interaction and long spin relaxation length in graphene. For implementation of practical and high-density graphene-based spintronic devices, we need to define nanoscale areas with room-temperature ferromagnetism on graphene. Here we report the room-temperature ferromagnetism observed in nanoscale functionalized (oxidized and hydrogenated) graphene using atomic force microscope lithography without involving potential surface contamination and chemical agents. By performing magnetic force microscope (MFM) measurements, we can clearly distinguish the local ferromagnetic signal of selectively functionalized graphene from that of surrounding non-magnetic pristine graphene. The nanoscale functionalized graphene shows experimental evidence of room-temperature ferromagnetism: (1) larger MFM signal than that of graphene; (2) repulsive and attractive interaction with an MFM tip the magnetization of which points into and out of the graphene, respectively; and (3) MFM signal reversal after applying a high magnetic field at an elevated temperature of 400 K. Our first-principles calculations reveal that unpaired spins are present at non-passivated dangling bonds of vacancies on functionalized graphene and the stable ferromagnetic exchange interactions between them are favored. Therefore, nanoscale functionalized graphene is a good candidate for use as the spin injector or detector of high-density graphene-based spintronic devices.

We investigated the subdomain structures of single-layer graphene oxide (GO) by characterizing local friction and conductance using conductive atomic force microscopy. Friction and conductance mapping showed that a single-layer GO flake has subdomains several tens to a few hundreds of nanometers in lateral size. The GO subdomains exhibited low friction (high conductance) in the sp(2)-rich phase and high friction (low conductance) in the sp(3)-rich phase. Current-voltage spectroscopy revealed that the local current flow in single-layer GO depends on the quantity of hydroxyl and carboxyl groups, and epoxy bridges within the 2-dimensional carbon layer. The presence of subdomains with different sp(2)/sp(3) carbon ratios on a GO flake was also confirmed by chemical mapping using scanning transmission X-ray microscopy. These results suggest that spatial mapping of the friction and conductance can be used to rapidly identify the composition of heterogeneous single-layer GO at nanometer scale, which is essential for understanding charge transport in nanoelectronic devices.

Strong charge-spin coupling is found in a layered transition-metal trichalcogenide NiPS3, a van derWaals antiferromagnet, from our study of the electronic structure using several experimental and theoretical tools: spectroscopic ellipsometry, x-ray absorption and photoemission spectroscopy, and density-functional calculations. NiPS3 displays an anomalous shift in the optical spectral weight at the magnetic ordering temperature, reflecting a strong coupling between the electronic and magnetic structures. X-ray absorption, photoemission and optical spectra support a self-doped ground state in NiPS3. Our work demonstrates that layered transition-metal trichalcogenide magnets are a useful candidate for the study of correlated-electron physics in two-dimensional magnetic material., Comment: 6 pages, 3 figure

In free space, unshielded large volume of a low permanent magnetic field (MF) generating system is necessary for use in such areas of magnetic measurements as: calibration of magnetometers, testing of materials, the ecological and medical effects, etc.

$M\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}g\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}c$ $c\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}y\phantom{\rule{0}{0ex}}s\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}s$ are metamaterials with engineered magnetic properties that can be used to manipulate spin waves, for next-generation digital logic and storage. Such an artificial crystal could be fashioned from arrays of magnetic $s\phantom{\rule{0}{0ex}}k\phantom{\rule{0}{0ex}}y\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}m\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}s$ (hedgehog-like topological objects), in principle. The authors show that by controlling the disposition of two lines of skyrmions with the asymmetric magnetic field from nearby currents, a spin wave could be refracted. This idea avoids the usual patterning of the magnonic crystal, which is the most time-consuming aspect of manufacturing.

We report on the structure and the magnetic properties of Bi1.985Cu0.015Te3 and Sb1.988-Cu0.012Te3 single crystals prepared using the temperature gradient solidification method. The crystals structure was rhombohedral, and the lattice constants decreased with the addition of Cu. The hole carrier conduction was observed in Hall-effect and thermopower measurements. The carrier densities and thermopowers at 300 K were 1.538 × 1020 cm−3/218.5 µV/K and 1.132 × 1021 cm−3/36.8 µV/K for Bi1.985Cu0.015Te3, and Sb1.988Cu0.012Te3, respectively. We could observe a strong diamagnetism with weak ferromagnetic hysteresis, indicating a mixture of non-magnetic and ferromagnetic ordering between Cu-ions in Bi2Te3 and Sb2Te3.

The one-dimensional magnetic skyrmion motion induced by an electric current has attracted much interest because of its application potential in next-generation magnetic memory devices. Recently, the unidirectional motion of large (20 μm in diameter) magnetic bubbles with two-dimensional skyrmion topology, driven by an oscillating magnetic field, has also been demonstrated. For application in high-density memory devices, it is preferable to reduce the size of skyrmion. Here we show by numerical simulation that a skyrmion of a few tens of nanometres can also be driven by high-frequency field oscillations, but with a different direction of motion from the in-plane component of the tilted oscillating field. We found that a high-frequency field for small skyrmions can excite skyrmion resonant modes and that a combination of different modes results in a final skyrmion motion with a helical trajectory. Because this helical motion depends on the frequency of the field, we can control both the speed and the direction of the skyrmion motion, which is a distinguishable characteristic compared with other methods.

Mn core-level spectra of Mn/Au(001) and Mn/Pt(001) systems are investigated by using X-ray photoemission spectroscopy. For the Mn/Au(001) system, large satellite structures which are very similar to those found previously in Mn/Cu(001) and Mn/Ag(001) systems, are also observed in the Mn 2p core level spectra. On the other hand, such large satellite structures are not observed in the case of the Mn/Pt(001) system. Considering the results of the structural analysis, these results indicate that the large satellite effect observed in Mn thin film systems is mainly related to the hybridization of Mn d electrons with the substrate, not to the effect of low-dimensionality as claimed in previous reports.

We investigated the field-effect transistor (FET) characteristics of 15-μm graphene-covered copper wires (G-wires). Unlike the previously reported graphene FET, carries initially showed p -type like FET characteristics in two-terminal transport measurements. Our results indicate that the electrical transport processes in a G-wire FET occur in both the heavily p -doped contact and the p -doped radial graphene channel, as a p -channel. The interfacial potential barrier between the contact electrode and the radial graphene channel is small, but there is a radial potential barrier that limits electrical transport through the copper core in chemical vapor deposition (CVD) grown samples. The p -type FET characteristics appeared clearly after the oxidation of the G-wires.

Adsorption of C 2 H 2 molecules on a Ge(1 0 0) surface at room temperature have been studied by ultraviolet photoelectron spectroscopy (UPS) using synchrotron radiation. In the UPS spectra, molecular orbitals (MOs) of the adsorbed C 2 H 2 as well as the Ge–C bonding states were identified. After annealing the C 2 H 2 -adsorbed surface causing partial desorption of the molecules, all the MOs were found to remain intact. In particular, the persistence of the π C – C orbitals after partial desorption comprises firm spectroscopic evidence against the existence of the so-called tetra- σ -bonded structure of the adsorbed C 2 H 2 molecules.

PGC1α protects against kidney injury by upregulating enzymes that enhance nicotinamide adenine dinucleotide (NAD) and driving local accumulation of the fatty acid breakdown product β-hydroxybutyrate, which leads to increased production of the renoprotective prostaglandin E2. Samir Parikh and colleagues show that the mitochondrial biogenesis regulator PGC1α protects against kidney injury by regulating NAD biosynthesis. In a mouse model, PGC1α upregulates NAMPT, an enzyme required form for NAD+ biosynthesis, and drives local accumulation of the fatty acid breakdown product β-hydroxybutyrate. This, in turn, leads to increased production of the renoprotective prostaglandin PGE2. The authors further show that treatment with the NAD precursor nicotinamide (NAM) can reverse established ischaemic kidney injury. The energetic burden of continuously concentrating solutes against gradients along the tubule may render the kidney especially vulnerable to ischaemia. Acute kidney injury (AKI) affects 3% of all hospitalized patients1,2. Here we show that the mitochondrial biogenesis regulator, PGC1α3,4, is a pivotal determinant of renal recovery from injury by regulating nicotinamide adenine dinucleotide (NAD) biosynthesis. Following renal ischaemia, Pgc1α−/− (also known as Ppargc1a−/−) mice develop local deficiency of the NAD precursor niacinamide (NAM, also known as nicotinamide), marked fat accumulation, and failure to re-establish normal function. Notably, exogenous NAM improves local NAD levels, fat accumulation, and renal function in post-ischaemic Pgc1α−/− mice. Inducible tubular transgenic mice (iNephPGC1α) recapitulate the effects of NAM supplementation, including more local NAD and less fat accumulation with better renal function after ischaemia. PGC1α coordinately upregulates the enzymes that synthesize NAD de novo from amino acids whereas PGC1α deficiency or AKI attenuates the de novo pathway. NAM enhances NAD via the enzyme NAMPT and augments production of the fat breakdown product β-hydroxybutyrate, leading to increased production of prostaglandin PGE2 (ref. 5), a secreted autacoid that maintains renal function. NAM treatment reverses established ischaemic AKI and also prevented AKI in an unrelated toxic model. Inhibition of β-hydroxybutyrate signalling or prostaglandin production similarly abolishes PGC1α-dependent renoprotection. Given the importance of mitochondrial health in ageing and the function of metabolically active organs, the results implicate NAM and NAD as key effectors for achieving PGC1α-dependent stress resistance.

Unidirectional motion of magnetic domain walls is the key concept underlying next-generation domain-wall-mediated memory and logic devices. Such motion has been achieved either by injecting large electric currents into nanowires or by employing domain-wall tension induced by sophisticated structural modulation. Herein, we demonstrate a new scheme without any current injection or structural modulation. This scheme utilizes the recently discovered chiral domain walls, which exhibit asymmetry in their speed with respect to magnetic fields. Because of this asymmetry, an alternating magnetic field results in the coherent motion of the domain walls in one direction. Such coherent unidirectional motion is achieved even for an array of magnetic bubble domains, enabling the design of a new device prototype—magnetic bubblecade memory—with two-dimensional data-storage capability.

Three-dimensional finite element analysis of arc-welding processes is presented with emphasis on practical applications for numerical simulation. We use an implicit numerical implementation for Leblond’s transformation plasticity constitutive equations, which are widely used in steel-structure welding. Several numerical examples, particularly including a large structure undergoing significant elastic–plastic deformations before welding, are presented to demonstrate the effectiveness of the three-dimensional analysis of welding processes.

Ultrathin Co films were deposited on Pt(100) at room temperature in ultrahigh vacuum, and investigated in situ by low-energy electron diffraction, scanning tunneling microscopy (STM), and surface magneto-optic Kerr effect. The Co film was grown into a wedge shape to provide a continuous change of the film thickness. We find that the Co film forms single-crystal ultrathin films at least up to 5 monolayers (ML). For as-grown films, we observe only in-plane magnetization. After annealing the film, the Co film develops a perpendicular magnetic anisotropy, leading to a spin reorientation transition at 2.7 ML Co thickness. STM measurements were performed at room temperature both before and after annealing the film. We found very different surface morphology and alloy formation after the film annealing, and attribute the perpendicular magnetic anisotropy to the formation of the Co-Pt alloy layer at the Co∕Pt(100) interface.Ultrathin Co films were deposited on Pt(100) at room temperature in ultrahigh vacuum, and investigated in situ by low-energy electron diffraction, scanning tunneling microscopy (STM), and surface magneto-optic Kerr effect. The Co film was grown into a wedge shape to provide a continuous change of the film thickness. We find that the Co film forms single-crystal ultrathin films at least up to 5 monolayers (ML). For as-grown films, we observe only in-plane magnetization. After annealing the film, the Co film develops a perpendicular magnetic anisotropy, leading to a spin reorientation transition at 2.7 ML Co thickness. STM measurements were performed at room temperature both before and after annealing the film. We found very different surface morphology and alloy formation after the film annealing, and attribute the perpendicular magnetic anisotropy to the formation of the Co-Pt alloy layer at the Co∕Pt(100) interface.

New evidence of the paired end-bridge configuration in the room-temperature adsorption geometries of C 2 H 2 molecules on Si(0 0 1) is presented by scanning tunneling microscopy (STM) and ab initio pseudopotential calculations. The distinct four-leaved feature occupying two adjacent Si dimer sites in the experimental empty-state STM images are well reproduced by simulations of the paired end-bridge adsorption configuration. Calculated energetics suggests that the Si(0 0 1) surface is covered by paired end-bridge structures at the saturation coverage of 1 ML, in agreement with the existing experiments.

We report the formation of atomically flat Si(0 0 1) surfaces with C incorporation using thermal dissociation of C 2 H 2 molecules. The resulting surface phases are investigated by scanning tunneling microscopy and found to contain C atoms as much as 0.2 monolayer (ML) without roughening. At low C concentrations, C-induced vacancy line defects are generated on the surface, forming a 2× n superstructure. As the C concentration increases, a new phase with a c(4×4) structure starts to appear and coexists with the 2× n phase, eventually covering the whole surface at about 0.2 ML. The C atoms in the 2× n superstructure are thought to occupy substitutional sites in a subsurface layer and constitute a δ-like distribution.

Acetylene molecules adsorbed on the Si(0 0 1) surface are studied by scanning tunneling microscope and ab initio pseudopotential calculations. In case of room-temperature adsorption, there are basically two different kinds of di-σ bonding geometries at low coverage: (i) on-top and (ii) end-bridge di-σ configurations. The tetra-σ configurations are not found. Theoretical calculations show that the paired end-bridge configuration is dominant at high coverage. Based on these findings, we discuss the results at saturation coverage in the existing literature consistently. Subsequent annealing of the C 2 H 2 /Si(0 0 1) surface induces different C-induced surface structures depending on the acetylene coverage. At low coverage, parallel lines of dimer vacancies are observed. As the amount of the adsorbed acetylene increases, the c(4×4) ordered phase replaces the dimer vacancy line phase. Near saturation, clusters are formed and the surface becomes rough.

High-performance ultra-thin oxide layers are required for various next-generation electronic and optical devices. In particular, ultra-thin resistive switching (RS) oxide layers are expected to become fundamental building blocks of three-dimensional high-density non-volatile memory devices. Until now, special deposition techniques have been introduced for realization of high-quality ultra-thin oxide layers. Here, we report that ultra-thin oxide layers with reliable RS behavior can be self-assembled by field-induced oxygen migration (FIOM) at the interface of an oxide-conductor/oxide-insulator or oxide-conductor/metal. The formation via FIOM of an ultra-thin oxide layer with a thickness of approximately 2-5 nm and 2.5% excess oxygen content is demonstrated using cross-sectional transmission electron microscopy and secondary ion mass spectroscopy depth profile. The observed RS behavior, such as the polarity dependent forming process, can be attributed to the formation of an ultra-thin oxide layer. In general, as oxygen ions are mobile in many oxide-conductors, FIOM can be used for the formation of ultra-thin oxide layers with desired properties at the interfaces or surfaces of oxide-conductors in high-performance oxide-based devices.

Nonlinear dynamics of the magnetic vortex state in a circular nanodisk was studied under a perpendicular alternating magnetic field that excites the radial modes of the magnetic resonance. Here, we show that as the oscillating frequency is swept down from a frequency higher than the eigenfrequency, the amplitude of the radial mode is almost doubled to the amplitude at the fixed resonance frequency. This amplitude has a hysteresis vs. frequency sweeping direction. Our result showed that this phenomenon was due to a Duffing-type nonlinear resonance. Consequently, the amplitude enhancement reduced the vortex core-switching magnetic field to well below 10 mT. A theoretical model corresponding to the Duffing oscillator was developed from the Landau–Lifshitz–Gilbert equation to explore the physical origin of the simulation result. This work provides a new pathway for the switching of the magnetic vortex core polarity in future magnetic storage devices.

The skyrmion magnetic bubble in a ferromagnetic disk exhibits hypocycloidal gyrations contrary to the vortex gyration, showing a simple circular trajectory. To describe the hypocycloidal bubble gyration, a mass term is needed in Thiele's equation. In this study, we analytically derived both mass and spring constant term, which are crucial parameters for describing the bubble gyration. Values obtained by these analytic expressions were consistent with those obtained by simulations. We could find the dependences of these two terms on several external parameters, including the bubble radius. Especially using the radius's dependence, we could obtain regular polygonlike trajectories such as a square and a triangle confirmed by the numerical simulations. Based on this effective method to control the bubble gyration, the regular polygonlike trajectories of this skyrmion magnetic bubble make it possible to study the bubble gyration without time-resolved experiments. © 2014 American Physical Society.

Unidirectional motion of magnetic domain walls is the key concept underlying next-generation domain-wall-mediated memory and logic devices. Such motion has been achieved either by injecting large electric currents into nanowires or by employing domain-wall tension induced by sophisticated structural modulation. Herein, we demonstrate a new scheme without any current injection or structural modulation. This scheme utilizes the recently discovered chiral domain walls, which exhibit asymmetry in their speed with respect to magnetic fields. Because of this asymmetry, an alternating magnetic field results in the coherent motion of the domain walls in one direction. Such coherent unidirectional motion is achieved even for an array of magnetic bubble domains, enabling the design of a new device prototype-magnetic bubblecade memory-with two-dimensional data-storage capability., Comment: 16 pages, 5 figures, ver.2: 2 supplementary movies

We measured geometric and magnetic properties of Co films on the Pd(1 1 1) surface by X-ray photoelectron diffraction (XPD), X-ray magnetic circular dichroism (MCD) at the Co L2,3 edge, and the surface magneto-optical Kerr effect (SMOKE) measurements. Co thin films are found to grow incoherently with fcc island structure on the smooth Pd(1 1 1) substrate. Comparison of MCD and SMOKE measurements of Co thin films grown on rough and smooth Pd(1 1 1) surfaces suggests that perpendicular remnant magnetization and Co orbital moment are enhanced by the rough interface. Pd capping layer also induces perpendicular orbital moment enhancement. These observations indicate the influence of hybridization between Co 3d and Pd 4d at the interface on the magnetic anisotropy.

Epitaxially c-axis oriented thin films of La0.7Ca0.3MnO3 (LCMO) have been fabricated on (001) SrTiO3 and (001) LaAlO3 substrates by pulsed laser-ablated deposition technique. The physical properties of as-grown films are correlated with the structural nature of the substrate. The O2-annealed films grown on both substrates exhibit higher metal-insulator (M-I) transition temperatures (TMI) and larger magnetoresistance (MR) ratios than the corresponding as-grown films. On the other hand, the Ar-annealed films display enhanced MR without any noticeable change in TMI. We suggest that increase in TMI is mainly ascribed to oxygen incorporation whereas enhancement of MR is largely associated with microstructural change induced by thermal annealing. Structural and transport data reveal that post-annealing with O2 not only saturates the anion defect sites but also relieves structural strain, resulting in the enhancement of TMI and large MR.

Low-energy electron diffraction I/V analyses reveal that Mn thin films deposited on Ag~001! at room temperature form substitutional, ordered, bilayer Mn 50Ag 50 surface alloys. The Mn atoms in this structure have local magnetic moments of considerable value, as judged from the Mn 3s core level spectra; these local magnetic moments of Mn are effective in the formation of the ordered surface alloy. Ab initio total energy calculations have been done and the results confirmed the experimental observations. @S0163-1829~98!03611-X#

Heat is a familiar form of energy transported from a hot side to a colder side of an object, but not a notion associated with microscopic measurements of electronic properties. A temperature difference within a material causes charge carriers, electrons or holes, to diffuse along the temperature gradient inducing a thermoelectric voltage. Here we show that local thermoelectric measurements can yield high sensitivity imaging of structural disorder on the atomic and nanometre scales. The thermopower measurement acts to amplify the variations in the local density of states at the Fermi-level, giving high differential contrast in thermoelectric signals. Using this imaging technique, we uncovered point defects in the first layer of epitaxial graphene, which generate soliton-like domain wall line patterns separating regions of the different interlayer stacking of the second graphene layer., Comment: Main Text (19 pages including 5 figures) + Supplementary Information (6 pages including 10 figures, simplified version)

We demonstrate that the controlled distribution of nanoparticles can be achieved by employing the spin-coating method. The Co and Ag nanoparticles were uniformly distributed on the Si and SiO2 substrates with this method. The particle density was controllable by varying the concentration of colloids. The spatial distribution of the nanoparticles within the patterned area was also shown to be uniform with small boundary effect, which is favorable for current microelectronics technology. We propose that the spin-coating method can be utilized in developing mass production processes for future nanodevices.

Epitaxial La0.7Ca0.3MnO3 thin films were grown on MgO (001) substrates by pulsed laser deposition. The as-grown films exhibit a metal–insulator transition at temperatures ranging from 200 to 230 K. Surprisingly, the transition temperature of postannealed films under O2 at 900 °C decreases by more than 100 K, featured with the colossal magnetoresistance. The O2 annealed films also show thermal hysteresis in resistivity and nonlinear I–V behavior. These results are interpreted in terms of Mn deficiency induced by large structural difference between film and substrate, and also discussed in viewpoint of a percolative phase transition.

Single-crystalline Fe/NiO bilayers were epitaxially grown on Ag(001) and on MgO(001), and investigated by low-energy electron-diffraction, magneto-optic Kerr effect, and x-ray magnetic linear dichroism (XMLD). We find that while the Fe film has an in-plane magnetization in both Fe/NiO/Ag(001) and Fe/NiO/MgO(001) systems, the NiO spin orientation changes from in-plane direction in Fe/NiO/Ag(001) to out-of-plane direction in Fe/NiO/MgO(001). These two different NiO spin orientations generate remarkable different effects that the NiO induced magnetic anisotropy in the Fe film is much greater in Fe/NiO/Ag(001) than in Fe/NiO/MgO(001). XMLD measurement shows that the much greater magnetic anisotropy in Fe/NiO/Ag(001) is due to a $90\ifmmode^\circ\else\textdegree\fi{}$ coupling between the in-plane NiO spins and the in-plane Fe spins.

In the present study, we propose a new methodology to develop the multi-parametric measure of heart rate variability (HRV) diagnosing cardiovascular disease using various linear and nonlinear measures of HRV. We recorded electrocardiogram for three recumbent postures; the supine, left lateral, and right lateral postures. Twenty control subjects, 51 patients with angina pectoris and 13 patients with acute coronary syndrome participated in this study. We used several time- and frequency-domain measures of HRV as linear measures. As nonlinear measures, Poincare plots, the fractal scaling measures and complexity estimations were used. To develop the multi-parametric measure of HRV, we used the multiple discriminant analysis method among statistical techniques. Multiple discriminant analysis was used to discriminate among three groups, i.e. control, angina pectoris and acute coronary syndrome. As a result, the multiple discriminant analysis gave 75.0 % of goodness of fit. In addition, the sensitivity and specificity for angina pectoris group are 72.5 % and 81.8 %, respectively. In the case of acute coronary syndrome group, the sensitivity and specificity are 84.6 % and 91.5 %, respectively. When the linear and nonlinear measures of HRV are individually used as a clinical tool to diagnose cardiac autonomic function, there is quite a possibility that the wrong results will be obtained due to each measure has different characteristics. Although our study is a preliminary one, we suggest that the multi-parametric measure, which takes into consideration the whole possible linear and nonlinear measures of HRV, may be helpful to diagnose the cardiovascular disease as a diagnostic supplementary tool.

We investigate the quantum-well states (QWSs) of Ag on an $\mathrm{Fe}\text{\ensuremath{-}}\mathrm{Ni}$ alloy film grown on a W(110) substrate, using spin- and angle-resolved photoemission spectroscopy (SPARPES). As the Ni content is increased, the $\mathrm{Fe}\text{\ensuremath{-}}\mathrm{Ni}$ alloy undergoes a transition from a bcc (110) structure to a fcc (111) structure at a Ni concentration of 30%. In the bcc (110) region, we found that as the Ni concentration was increased, the binding energy shifted linearly toward higher binding energy in the QWSs of a thin Ag film, with a maximum shift of $0.4\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ for a Ni concentration of 30%. Our SPARPES data and phase accumulation model calculation indicate that this shift is due to electron doping resulting from inserting Ni, which has two more electrons than Fe. In the fcc (111) region, by contrast, the binding energy shift in the QWSs is barely noticeable, indicating that the potential shift caused by electron doping is insufficiently large in this region. Moreover, as the Ni concentration is increased, a decrease in the polarization of QWSs is observed, which can be attributed to the reduced exchange splitting energy.

The C amount and the structure of the $\mathrm{S}\mathrm{i}(001)\mathrm{\text{\ensuremath{-}}}c(4\ifmmode\times\else\texttimes\fi{}4)$ surface is studied using scanning tunneling microscopy (STM) and ab initio calculations. The $c(4\ifmmode\times\else\texttimes\fi{}4)$ phase is found to contain $1/8$ monolayer C (1 C atom in each primitive unit cell). From the C amount and the symmetry of high-resolution STM images, it is inferred that the C atoms substitute the fourth-layer site below the dimer row. We construct a structure model relying on ab initio energetics and STM simulations. Each C atom induces an on-site dimer vacancy and two adjacent rotated dimers on the same dimer row. The $c(4\ifmmode\times\else\texttimes\fi{}4)$ phase constitutes the subsurface ${\mathrm{S}\mathrm{i}}_{0.875}{\mathrm{C}}_{0.125}$ $\ensuremath{\delta}$ layer with two-dimensionally ordered C atoms.