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The electrical ferromagnetic resonance of micro-scale Ni wires with magnetic anisotropy induced by the heterojunction between the Ni layer and ferroelectric single crystalline LiNbO3 substrate was demonstrated by using rectifying effect. The two resonance modes were observed in the Ni wire aligned parallel to the applied magnetic field in plane. The lower resonance frequency mode is considered to correspond to the normal resonance mode with domain resonance, while the higher resonance mode is attributed to the mode which is contributed by the heterojunction between the Ni layer and LiNbO3 substrate. Our results manifest that the rectifying electrical detections are very useful for understating and evaluating the magnetic properties induced by the heterojunction.

A synchrotron radiation photoemission electron microscope (SR-PEEM) was applied to demonstrate the pinpoint analysis of micrometer-sized weathered biotite clay particles with artificially adsorbed cesium (Cs) atoms. Despite the insulating properties of the clay, we observed the spatial distributions of constituent elements (Si, Al, Cs, Mg, and Fe) without charging issues and clarified reciprocal site-correlations among these elements with nanometer resolution. We found that Cs atoms were likely to be adsorbed evenly over the entire particle; however, we identified an occupational conflict between Cs and Mg atoms, implying that Cs sorption involves ion exchange processes. Spatially resolved X-ray absorption spectra (XAS) of the Cs4,5 M-edge region showed Cs to be present in a monocation state (Cs+) as typically observed for Cs compounds. Further pinpoint XAS measurements were also performed at the Fe L2,3-edge to determine the chemical valence of the Fe atoms. The shapes of the spectra were similar to those for Fe2O3, indicating that Fe in the clay was in a 3+ oxidation state. From these observations, we infer that charge compensation facilitates Cs adsorption in the vicinity of a substitution site where Si4+ ions are replaced by Fe3+ ions in SiO4 tetrahedral sheets. Our results demonstrate the utility of SR-PEEM as a tool for spatially resolved chemical analyses of various environmental substances, which is not limited by the poor conductivity of samples.

We have performed x-ray photoemission spectroscopy (XPS), x-ray absorption spectroscopy (XAS), and resonant photoemission spectroscopy (RPES) measurements of Mn-implanted 3$C$-SiC (3$C$-SiC:Mn) and carbon-incorporated Mn$_{5}$Si$_{2}$ (Mn$_{5}$Si$_{2}$:C). The Mn 2$p$ core-level XPS and XAS spectra of 3$C$-SiC:Mn and Mn$_{5}$Si$_{2}$:C were similar to each other and showed "intermediate" behaviors between the localized and itinerant Mn 3$d$ states. The intensity at the Fermi level was found to be suppressed in 3$C$-SiC:Mn compared with Mn$_{5}$Si$_{2}$:C. These observations are consistent with the formation of Mn$_{5}$Si$_{2}$:C clusters in the 3$C$-SiC host, as observed in a recent transmission electron microscopy study., Comment: 4 pages, 3 figures

Resonant X-ray magnetic diffraction profiles were measured for an epitaxial Fe/Cu multilayer using circularly polarized X-rays near the Fe and Cu K-edges. Diffraction intensities were compared with those obtained from the theoretical and empirical models. It is found that the interface Fe moment is reduced to 70% of the inner-layer moment. Concerning the Cu layer, the observed energy dependence of the magnetic diffraction intensities is consistent with that derived from the first-principle band calculation, indicating that magnetic proximity effect in the Cu layer is confined within a few atomic layers near the interface.

The characteristics of a coarse-grained high-remanence magnetite obtained from shocked Vredefort granite were investigated by X-ray magnetic circular dichroism (XMCD) analysis and X-ray absorption spectroscopy (XAS). The study utilized a spectroscopic photoelectron low-energy electron emission microscope (SPELEEM) and was conducted in the SPring-8 large-synchrotron radiation facility. It is generally believed that the strong and stable bulk remanence of Vredefort granites is due to the presence of minerals that have been strongly magnetized by either an impact-generated magnetic field or terrestrial lightning strikes. Although coarse-grained magnetite is traditionally characterized by weak coercivity and remanence, the specimen used in the present study exhibited high coercivity and an intense remanent magnetization. The presence of hematite lamellae observed on the partially oxidized magnetite specimen indicated an array of striped domains, intensifying a remanence and coercivity. We also conducted XAS and XMCD analyses on a natural lodestone permanent magnet produced by lightning strikes; while maghemite was found to be present, no magnetic domain structures were observed. Considering that the nucleation of hematite lamellae on magnetite/maghemite grains is due to high-temperature oxidation, we attribute the intense remanent magnetization and magnetic hardening of Vredefort granites to post-impact hydrothermal activity.

The electronic structures of the ferromagnetic superconductors ${\mathrm{UGe}}_{2}$ and $\mathrm{UCoGe}$ in the paramagnetic phase were studied by angle-resolved photoelectron spectroscopy using soft x rays $(h\ensuremath{\nu}=400\text{--}500\phantom{\rule{0.28em}{0ex}}\mathrm{eV})$. The quasiparticle bands with large contributions from $\mathrm{U}\phantom{\rule{0.28em}{0ex}}5f$ states were observed in the vicinity of ${E}_{\mathrm{F}}$, suggesting that the $\mathrm{U}\phantom{\rule{0.28em}{0ex}}5f$ electrons of these compounds have an itinerant character. Their overall band structures were explained by the band-structure calculations treating all the $\mathrm{U}\phantom{\rule{0.28em}{0ex}}5f$ electrons as being itinerant. Meanwhile, the states in the vicinity of ${E}_{\mathrm{F}}$ show considerable deviations from the results of band-structure calculations, suggesting that the shapes of Fermi surface of these compounds are qualitatively different from the calculations, possibly caused by electron correlation effect in the complicated band structures of the low-symmetry crystals. Strong hybridization between $\mathrm{U}\phantom{\rule{0.28em}{0ex}}5f$ and $\mathrm{Co}\phantom{\rule{0.28em}{0ex}}3d$ states in $\mathrm{UCoGe}$ were found by the $\mathrm{Co}\phantom{\rule{0.28em}{0ex}}2p\ensuremath{-}3d$ resonant photoemission experiment, suggesting that $\mathrm{Co}\phantom{\rule{0.28em}{0ex}}3d$ states have finite contributions to the magnetic, transport, and superconducting properties.

Depth-resolved induced magnetic polarization in the Cu layer of the [Gd (57.4 A)/Cu (16.5 A)] multilayer is determined by resonant X-ray magnetic diffraction technique. The X-ray energy was tuned near the Cu K absorption edge (8981 eV). The resonant magnetic diffraction peaks from second to fourth order were measured at 10 and 75 K by helicity switching combined with field reversal. The analysis indicates that the induced magnetic polarization extends to the center of the Cu layer and that the magnetization polarization distribution scaled to the Gd magnetization is unchanged against temperature. The shape of the magnetic polarization distribution in the Gd/Cu multilayer is different from that predicted theoretically in the Co/Cu multilayer, where the induced magnetic polarization is concentrated mainly at the interface. A possible reason for the different distribution of the magnetic polarization in the Gd/Cu and Co/Cu systems is discussed.

We performed 119Sn Mossbauer spectroscopic measurements on Gd/Cu multilayers with 119Sn probing atoms. The Cu layers are delta-doped with Sn probes at a certain depth. Hyperfine fields are observed in the Mossbauer spectra at low temperatures below the Curie temperature of the Gd layers. From the temperature-dependent measurements, the hyperfine field is found to be proportional to the spontaneous magnetization of the Gd layer. The result indicates that the Gd magnetization induces magnetic polarization in the Cu layers. The hyperfine field per Gd magnetization is found to be ~40 kOe /μB(Gd), regardless of the position of the 119Sn atoms and the Cu thickness (20–40 A), suggesting that the magnetic polarization in the Cu layer is uniform at any depth from the Gd/Cu interface.

The induced magnetic polarization in nonmagnetic layers and its relationship with the magnetization in ferromagnetic layers are investigated for Gd/Cu multilayers with X-ray magnetic circular dichorism (XMCD). The XMCD measurements show that the peak intensities at the Cu K -edge decrease in proportion to those at the Gd L 3 -edge as the temperature increases. The overall shape of the XMCD spectra at the Cu K -edge, on the other hand, does not change. These results suggest that the size of the magnetic polarization in the Cu layers changes but the depth profile remains unchanged when the Gd magnetization varies in size. The XMCD spectra at the Cu K -edge are composed of several positive and negative peaks. A possible origin of the specific shape of the spectra is discussed.

Deployments of spherical grids to obtain high energy and angular resolutions for retarding field analyzers (RFAs) having acceptance angles as large as or larger than ±45° were explored under the condition of using commercially available microchannel plates with effective diameters of approximately 100 mm. As a result of electron trajectory simulations, a deployment of three spherical grids with significantly different grid separations instead of conventional equidistant separations showed an energy resolving power (E/ΔE) of 3200 and an angular resolution of 0.6°. The mesh number of the wire mesh retarding grid used for the simulation was 250. An RFA constructed with the simulated design experimentally showed an E/ΔE of 1100 and an angular resolution of 1°. Using the RFA and synchrotron radiation of 900 eV, photoelectron diffraction (PED) measurements were performed for single-crystal graphite. A clear C 1s PED pattern was observed even when the differential energy of the RFA was set at 0.5 eV. Further improvement of the energy resolution was theoretically examined under the assumption of utilizing a retarding grid fabricated by making a large number of radially directed cylindrical holes through a partial spherical shell instead of using a wire mesh retarding grid. An E/ΔE of 14 500 was predicted for a hole design with a diameter of 60 μm and a depth of 100 μm. A retarding grid with this hole design and a holed area corresponding to an acceptance angle of ±7° was fabricated. An RFA constructed with this retarding grid experimentally showed an E/ΔE of 1800. Possible reasons for the experimental E/ΔE lower than the theoretical values are discussed.

Perpendicularly magnetized ferrimagnetic Gd–Fe–Co thin films with different compositions and multilayer arrangements were subjected to femtosecond laser pulses. The pulses triggered different magnetization dynamics in the various thin films. In the Gd26Fe66Co8 film, which has an angular-momentum-compensation temperature (T A) well above ambient temperature (T exp), monotonic magnetization reversal occurred, whereas the Gd22Fe70Co8 film (where T A is well below T exp) exhibited remarkable wavelike spin modulation with spatial inhomogeneity during relaxation of the laser-induced nonequilibrium state. These findings can enable broad-range tuning of the magneto-optical responses of Gd–Fe–Co alloys, facilitating advances in materials engineering.

Graphene exhibits unusual electronic properties, caused by a linear band structure near the Dirac point. This band structure is determined by the stacking sequence in graphene multilayers. Here we present a novel method of microscopically controlling the band structure. This is achieved by epitaxy of graphene on 3C-SiC(111) and 3C-SiC(100) thin films grown on a 3D microfabricated Si(100) substrate (3D-GOS (graphene on silicon)) by anisotropic etching, which produces Si(111) microfacets as well as major Si(100) microterraces. We show that tuning of the interface between the graphene and the 3C-SiC microfacets enables microscopic control of stacking and ultimately of the band structure of 3D-GOS, which is typified by the selective emergence of semiconducting and metallic behaviours on the (111) and (100) portions, respectively. The use of 3D-GOS is thus effective in microscopically unlocking various potentials of graphene depending on the application target, such as electronic or photonic devices.

Angle-resolved photoelectron spectroscopy (ARPES) measurements were made in the Ce 3d → 4f resonance energy region for the paramagnetic state of CeRu 2 Si 2 , CeRu 2 (Si 0.82 Ge 0.18 ) 2 , and LaRu 2 Si 2 to investigate a variation of band structures around the quantum critical point (QCP). The observed band structures are very similar between CeRu 2 Si 2 and CeRu 2 (Si 0.82 Ge 0.18 ) 2 . The results indicate that the Ce 4f electrons in the paramagnetic state have an itinerant character and participate in the formation of energy bands both in CeRu 2 Si 2 and CeRu 2 (Si 0.82 Ge 0.18 ) 2 , and the change of the band structures in the paramagnetic states should be continuous around the QCP of the CeRu 2 (Si 1-x Ge x ) 2 system.

The intrinsic transport properties, such as carrier mobility and saturation velocity, of graphene are the highest among materials owing to its linear band dispersion and weak backscattering. However, the reported field-effect mobility of transistors using graphene as a channel is much lower than the intrinsic channel mobility. One of the reasons for this low mobility is the high contact resistance between graphene and metals used for the source and drain electrodes, which results from the interfacial roughness. Even Ni, which is a promising contact metal for many materials because of its high adhesion and lower contact resistance, does not meet the requirement as a contact metal for graphene. Noticing that the interfacial roughness between the a metal and graphene is strongly related to the onset of the contact resistance, we performed transmission electron microscopy and photoemission electron microscopy measurements to evaluate the microscopic lateral and longitudinal distributions of Ni atoms at the Ni...

We demonstrate the time-resolved real-space observation of vortex gyration in a magnetic circular disc by X-ray magnetic circular dichroism photoemission microscopy at the SPring-8 beamline BL25SU, both with and without an additional structure called a pair tag, which serves to control the magnetic curling direction. By comparing the gyration orbits of the vortices, we found that the gyration properties are dependent on the presence of the additional structure in spite of the discs having the same diameter. Furthermore, we reproduced the vortex gyration by micromagnetic simulation. The confinement potential of the vortex can be controlled by the additional structure.

The electronic structure of the antiferromagnet uranium nitride (UN) has been studied by angle resolved photoelectron spectroscopy using soft X-rays (hn=420-520 eV). Strongly dispersive bands with large contributions from the U 5f states were observed in ARPES spectra, and form Fermi surfaces. The band structure as well as the Fermi surfaces in the paramagnetic phase are well explained by the band-structure calculation treating all the U 5f electrons as being itinerant, suggesting that itinerant description of the U 5f states is appropriate for this compound. On the other hand, changes in the spectral function due to the antiferromagnetic transition were very small. The shapes of the Fermi surfaces in a paramagnetic phase are highly three-dimensional, and the nesting of Fermi surfaces is unlikely as the origin of the magnetic ordering., 8 pages, 5 figures, Phys. Rev. B in press

A determination of the three-dimensional spin directions in all types of domain walls (DWs) of antiferromagnetic NiO has been successfully performed by photoemission electron microscopy combined with x-ray magnetic linear dichroism (XMLD), both for $s$- and $p$-polarized light. By comparing the azimuthal angle dependence of the XMLD contrast in the DWs with cluster model calculations which include the crystal symmetry and full-multiplet splitting, we determine the spin structures in the ${001}$ T walls, ${011}$ T walls, 120\ifmmode^\circ\else\textdegree\fi{} S walls, and 180\ifmmode^\circ\else\textdegree\fi{} S walls. In some cases, distinct S walls are not formed between two adjacent S domains, and the spin direction changes gradually over a wide range of the S domain structures. In the S walls, the spin direction is parallel to the magnetic easy ${111}$ plane. These spin configurations arise from the large difference in anisotropy energy between the in-plane and out-of-plane directions. Unexpectedly large widths in the several hundred nanometer range were observed for all the DWs. This also shows that NiO has a small magnetocrystalline anisotropy energy. Together with Monte Carlo simulation results, the qualitative phenomena concerning the wall energies are discussed. We further investigated the difference in wall energy between the ${001}$ T wall and the ${011}$ T wall. From the Monte Carlo simulation and an experimental study of heating effects, it is revealed that the ${001}$ T wall energy is smaller than the ${011}$ T wall energy.

We have investigated the electronic structure of ZnO:Mn and ZnO:Mn,N thin films using x-ray magnetic circular dichroism (XMCD) and resonance-photoemission spectroscopy. From the Mn 2$p$$\rightarrow3d$ XMCD results, it is shown that, while XMCD signals only due to paramagnetic Mn$^{2+}$ ions were observed in ZnO:Mn, nonmagnetic, paramagnetic and ferromagnetic Mn$^{2+}$ ions coexist in ZnO:Mn,N. XMCD signals of ZnO:Mn,N revealed that the localized Mn$^{2+}$ ground state and Mn$^{2+}$ state hybridized with ligand hole coexisted, implying $p$-$d$ exchange coupling. In the valence-band spectra, spectral weight near the Fermi level was suppressed, suggesting that interaction between magnetic moments in ZnO:Mn,N has localized nature., Comment: 4 figures

We have studied conduction-band (CB) electronic states of a typical valence-transition compound YbInCu4 by means of temperature-dependent hard x-ray photoemission spectroscopy (HX-PES) of the Cu 2p3/2 and In 3d5/2 core states taken at hν = 5.95 keV, soft x-ray absorption spectroscopy (XAS) of the Cu 2p3/2 core absorption region around hν ∼ 935 eV, and soft x-ray photoemission spectroscopy (SX-PES) of the valence band at the Cu 2p3/2 absorption edge of hν = 933.0 eV. With decreasing temperature below the valence transition at TV = 42 K, we have found that (1) the Cu 2p3/2 and In 3d5/2 peaks in the HX-PES spectra exhibit the energy shift toward the lower binding-energy side by ∼40 and ∼30 meV, respectively, (2) an energy position of the Cu 2p3/2 main absorption peak in the XAS spectrum is shifted toward higher photon-energy side by ∼100 meV, with an appearance of a shoulder structure below the Cu 2p3/2 main absorption peak, and (3) an intensity of the Cu L3VV Auger spectrum is abruptly enhanced. These experimental results suggest that the Fermi level of the CB-derived density of states is shifted toward the lower binding-energy side. We have described the valence transition in YbInCu4 in terms of the charge transfer from the CB to Yb 4f states.

Micrometre-size lateral magnetic modulations were fabricated in FeRh thin films by ion-microbeam irradiation. Their magnetic domain structures were characterized by XMCD–PEEM., FeRh thin films were irradiated with a 10 MeV iodine ion microbeam to produce micrometre-scale ferromagnetic microstructures by modifying the local magnetic character from antiferromagnetism to ferromagnetism using ion-microbeam irradiation. Two-dimensional magnetic dot arrays of dimensions ∼2 µm × 4 µm as well as 10 µm × 10 µm were successfully produced on the FeRh surface, which was confirmed by magnetic force microscopy (MFM). The results of photoemission electron microscopy (PEEM) combined with X-ray magnetic circular dichroism reveal that the easy axis of the magnetization of the ion-beam-irradiated ferromagnetism in the FeRh thin films lies in the film planes along the 〈001〉 direction of the MgO substrates.

We have investigated the electronic states of the uranium monochalcogenide US, which is a typical ferromagnetic uranium compound, using soft x-ray photoemission spectroscopy (SX-PES). In early ultraviolet photoemission spectroscopy studies, two peak structures of the $\text{U}\text{ }5f$ states were observed and have been interpreted that one has an itinerant character around the Fermi level $({E}_{\text{F}})$ and the other located below ${E}_{\text{F}}$ has a character of localized $\text{U}\text{ }5f$ electrons. In this study, the intrinsic bulk valence-band spectrum of US was first deduced by estimating the contribution of surface states to the valence-band spectrum using core-level photoemission spectra. We conclude that the electronic structure of US can be basically described by the itinerant nature of the $\text{U}\text{ }5f$ electrons from comparison with theoretical valence-band spectra obtained by band-structure calculation in the local-density approximation.

X-ray magnetic circular dichroism (XMCD) experiments were performed at the $\text{Np}\text{ }{M}_{4,5}$ and the $\text{Ga}\text{ }K$ absorption edges of ${\text{NpNiGa}}_{5}$ to investigate the temperature-dependent changes of magnetic properties of $\text{Np}\text{ }5f$ and $\text{Ga}\text{ }4p$ electron states. By the sum-rule analysis of the $\text{Np}\text{ }{M}_{4,5}$ XMCD data, the orbital magnetic moment ${\ensuremath{\mu}}_{L}$ and the spin magnetic moment ${\ensuremath{\mu}}_{S}$ were estimated for the $\text{Np}\text{ }5{f}^{3}$ and $5{f}^{4}$ electronic configurations and their comparison to the previous magnetization and neutron-scattering experiments suggests that the $5{f}^{4}$ configuration is more likely than the $5{f}^{3}$ configuration in ${\text{NpNiGa}}_{5}$. It was found that $|{\ensuremath{\mu}}_{L}/{\ensuremath{\mu}}_{S}|$ tends to increase from the high-temperature low-moment ordered state to the low-temperature high-moment ordered state. The result of the $\text{Ga}\text{ }K$ XMCD indicates that the $\text{Ga}\text{ }4p$ electrons are magnetically polarized and the temperature and magnetic-field dependences of the $\text{Ga}\text{ }4p$ orbital moment are proportional to those of the magnetization measurements.

Angle-resolved photoelectron spectroscopy in the Ce $3d\ensuremath{\rightarrow}4f$ excitation region was measured for the paramagnetic state of ${\mathrm{CeRu}}_{2}{\mathrm{Si}}_{2}$, ${\mathrm{CeRu}}_{2}({\mathrm{Si}}_{0.82}{\mathrm{Ge}}_{0.18}{)}_{2}$, and ${\mathrm{LaRu}}_{2}{\mathrm{Si}}_{2}$ to investigate the changes of the $4f$ electron Fermi surfaces around the quantum critical point. While the difference of the Fermi surfaces between ${\mathrm{CeRu}}_{2}{\mathrm{Si}}_{2}$ and ${\mathrm{LaRu}}_{2}{\mathrm{Si}}_{2}$ was experimentally confirmed, a strong $4f$-electron character was observed in the band structures and the Fermi surfaces of ${\mathrm{CeRu}}_{2}{\mathrm{Si}}_{2}$ and ${\mathrm{CeRu}}_{2}({\mathrm{Si}}_{0.82}{\mathrm{Ge}}_{0.18}{)}_{2}$, consequently indicating a delocalized nature of the $4f$ electrons in both compounds. The absence of Fermi surface reconstruction across the critical composition suggests that SDW quantum criticality is more appropriate than local quantum criticality in ${\mathrm{CeRu}}_{2}({\mathrm{Si}}_{1\ensuremath{-}x}{\mathrm{Ge}}_{x}{)}_{2}$.

The electronic structure of In2-xVxO3 (x=0.08) has been investigated by photoemission spectroscopy and x-ray absorption spectroscopy (XAS). The V 2p core-level photoemission and XAS spectra reveale ...

We have studied the electronic structure of Zn$_{0.9}$Fe$_{0.1}$O nano-particles, which have been reported to show ferromagnetism at room temperature, by x-ray photoemission spectroscopy (XPS), resonant photoemission spectroscopy (RPES), x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD). From the experimental and cluster-model calculation results, we find that Fe atoms are predominantly in the Fe$^{3+}$ ionic state with mixture of a small amount of Fe$^{2+}$ and that Fe$^{3+}$ ions are dominant in the surface region of the nano-particles. It is shown that the room temperature ferromagnetism in the Zn$_{0.9}$Fe$_{0.1}$O nano-particles is primarily originated from the antiferromagnetic coupling between unequal amounts of Fe$^{3+}$ ions occupying two sets of nonequivalent positions in the region of the XMCD probing depth of $\sim$ 2-3 nm., Comment: Single column, 12 pages, 8 figures, 1 table

We have derived the three-dimensional band structure and Fermi surfaces of itinerant uranium compound ${\text{UB}}_{2}$ by soft x-ray angle-resolved photoelectron spectroscopy. We have observed clear energy dispersions and Fermi surfaces with large contribution from the $\text{U}\text{ }5f$ states. The obtained results have been compared with the result of band-structure calculation within the local-density-functional approximation as well as the results of de Haas--van Alphen (dHvA) study. The qualitative agreement has been obtained in the size and topology of the Fermi surfaces with the band-structure calculation and the dHvA measurement. Meanwhile, their band structure near the Fermi level is slightly different from the calculation. This might be due to a dynamic renormalization beyond the local-density approximation band calculations even in the very itinerant $5f$ compound.

The magnetic properties of as-grown Ga1-xMnxAs have been investigated by the systematic measurements of temperature and magnetic field dependent soft x-ray magnetic circular dichroism (XMCD). The intrinsic XMCD intensity at high temperatures obeys the Curie-Weiss law, but a residual spin magnetic moment appears already around 100 K, significantly above the Curie temperature (T_{C}), suggesting that short-range ferromagnetic correlations are developed above T_{C}. The present results also suggest that the antiferromagnetic interaction between the substitutional and interstitial Mn (Mn_{int}) ions exists and that the amount of the Mn_{int} affects T_{C}.

High quality epitaxial SrCoO x (oxygen deficient SrCoO 3 ) thin films were grown on (110) DyScO3 substrates by pulsed laser deposition.The disappearance of half order peaks in X-ray diffraction as well as the XAS at the O K-edge indicates an oxygen content of x ≈ 2.8 in the thin films. Magnetization measurements reveal that the specific substrate strain suppresses the ferromagnetism found in the corresponding bulk material and the emergence of an antiferromagnetic-type spin correlation as predicted by theoretical calculations. Our work demonstrates that the magnetism can be tuned by in-plane strain in SrCoO x thin films.

The behavior of a three-terminal domain wall (DW) device with a perpendicularly magnetized CoFeB free layer and underlying hard magnets was investigated. In a Ta/CoFeB/MgO free layer without hard magnets, a current-induced DW motion in the direction of electron flow was observed. In a device having a hard magnet under each end of the free layer, we found that a DW nucleated by injecting current played an important role in the switching of magnetization. We concluded that the switching of magnetization in our device is due to the displacement in the direction of electron flow of the DW created by current. After deriving the principle of operation through experiments, we describe a way to reduce the current required for writing by increasing the thickness of the hard magnets.

It is known that spin polarization induced in the Au layers of Fe/Au multilayers which show interlayer exchange coupling consists of an interface-concentrated component and a uniformly extended interior component. To investigate the origin of the interior component, magnetic depth profiles of spin polarization induced in the Au layers of Fe (15 A)/Au (50 A) bilayer and Fe (15 A)/Au (50 A)/Fe (15 A) trilayer films were investigated with resonant X-ray magnetic reflectivity (RXMR) measurements at the Au L3 absorption edge. After the determination of charge structures, the spin attenuation length for the interior component of the bilayer sample was evaluated to be longer than 15 A from the analysis of the RXMR pattern. The RXMR pattern of the trilayer sample was not sufficiently reproduced if the magnetic structure of the trilayer sample was assumed to be a simple sum of the magnetic structure obtained from the bilayer sample. Results were discussed based on the quantum well model.

FeCo thin films are fabricated by alternate monoatomic layer deposition method on a Cu3Au buffer layer, which in-plane lattice constant is very close to the predicted value to obtain a large magnetic anisotropy constant. The variation of the in-plane lattice constant during the deposition process is investigated by reflection high-energy electron diffraction. The magnetic domain images are also observed by a photoelectron emission microscope in order to microscopically understand the magnetic structure. As a result, element-specific magnetic domain images show that Fe and Co magnetic moments align parallel. A series of images obtained with various azimuth reveal that the FeCo thin films show fourfold in-plane magnetic anisotropy along ⟨110⟩ direction, and that the magnetic domain structure is composed only of 90∘ wall.

To understand the hard magnetism of L10-type ordered FeNi alloy, we extracted the L10-FeNi phase from a natural meteorite, and evaluated its fundamental solid-state properties: sample composition, magnetic hysteresis, crystal structure and electronic structure. We executed multidirectional analyses using scanning electron microscopy with an electron probe micro-analyzer (SEM-EPMA), a superconducting quantum interference device (SQUID), x-ray diffraction (XRD) and magnetic circular dichroism (MCD). As a result, we found that the composition was Fe: 50.47 ± 1.98 at.%, Ni: 49.60 ± 1.49 at.%, and an obvious superlattice peak is confirmed. The estimated degree of order was 0.608, with lattice constants a = b = 3.582 Å and c = 3.607 Å. The obtained coercivity was more than 500 Oe. MCD analysis using the K absorption edge suggests that the magnetic anisotropy could originate from the orbital magnetic moment of 3d electrons in Fe; this result is consistent with that in a previous report obtained with synthetic L10-FeNi.

The resistive switching characteristics of a TiO2/Ti structure have been investigated using a conductive atomic force microscopy (AFM) system with 5-nm-diameter carbon nanotube (CNT) probes. The resistive switching showed bipolar resistive random access memory (ReRAM) behaviors with extremely low switching currents in the order of Picoamperes when voltages were applied. From transmission electron microscopy (TEM) observation, we confirmed that filament-like nanocrystals, having a diameter of about 10 nm, existed in TiO2 films at resistive switching areas after not only set operation but also reset operation. Moreover, photoemission electron microscopy (PEEM) analysis showed that the anatase-type TiO2 structure did not change after set and reset operations. From these results, we suggested that the Picoampere resistive switching occurred at the interface between the TiO2 dielectric and conductive nanocrystal without any structural changes in the TiO2 film and nanocrystal. The resistive switching mechanism we suggested is highly promising to realize extremely low-power-consumption ReRAMs with vertically contacted CNT electrodes.

Photoelectron emission microscopy observation is performed on an FeNi alloy processed by high-pressure torsion (HPT) in order to microscopically analyze magnetic domain structure, elemental distribution, and surface morphology. While belt-like magnetic domain structures with widths of 3 to 5 μm are observed at about 2 mm away from the sample disc center, only narrower magnetic domain structure is observed at 1 mm away from the disc center. While these magnetic domain structures are related to a product during the HPT process, they are related neither to inhomogeneity of elemental distribution nor to surface morphology. Therefore, it is suggested that the observed magnetic domains should be originated from an L10 phase. The present analysis indicates that atomic diffusion is significantly enhanced by processing the samples with HPT and post-annealing.

Spin polarization of 5d conduction electrons induced in the Au layers of antiferromagnetically coupled Fe/Au metallic superlattice was investigated by resonant X-ray magnetic diffraction at the Au L3 absorption edge. Superlattice reflections around the Au 002 Bragg peak were measured in the magnetic saturation state with circularly polarized synchrotron radiation X-rays of 11921 eV. The magnetic diffraction profile was extracted with the combination of helicity switching and reversing the direction of magnetic field applied along the line of intersection between the film surface and the scattering plane. The depth distribution of resonant magnetic scattering length in the Au layers was estimated from the magnetic diffraction profile. Both resonant magnetic diffraction from the Au layer and non-resonant magnetic diffraction from the Fe layer were considered in the analysis. We demonstrated that the depth distribution of the Au magnetic scattering length was expressed with sum of the interface-concentrated ...

Examples of the application of photoelectron emission microscopy (PEEM) combined with synchrotron radiation excitation are reviewed. In particular, the combination study of PEEM and X-ray magnetic dichroism spectroscopy is very valuable for magnetic domain imaging. According to the demands of the industry, such as the production of magnetic recording media, the application method becomes very important. In this review, several examples of studies using magnetic circular and/or linear dichroism spectroscopy for ferro- and antiferromagnetic materials are introduced. In addition, pump–probe time-resolved PEEM is introduced. These methods allow us to measure the dynamical motion of micro-magnetic structures in mesoscopic size magnets in response to the field pulse in the sub-nanosecond range.

We developed a system to carry out time-resolved photoemission electron microscopy under RF excitation at the BL25SU beamline in SPring-8. RF fields of up to ∼42 MHz could be applied to microsized magnetic disks with a power loss of less than 0.9 dB. We performed time-resolved real-space observations of the gyrotropic motion of the magnetic vortex core in Ni81Fe19 disks under an RF magnetic field. We confirmed that significant core gyrations can be seen only when the resonant frequency of the disks matches with the excitation frequency of the system.

By means of soft X-ray photoemission electron microscopy (PEEM), we have for the first time observed spatially and temporally resolved element-specific magnetization switching driven by circularly polarized femtosecond laser pulses. We have confirmed that the magnetization switching depending on the helicity of the circularly polarized laser occurs in the region where the spin temperature is raised appropriately. It is also found that the electronic states in the irradiated region remain unchanged even after millions magnetization reversal cycles.

The epitaxy of graphene on 3C-SiC(111) formed on microfabricated Si(111) has been demonstrated. Through observations by optical microscopy, micro-Raman spectroscopy, low-energy electron diffraction, and photoelectron spectroscopy, it has been confirmed that the epitaxial graphene is Bernal-stacked with a buffer layer present between graphene and the 3C-SiC film, which can lead to the opening of the band gap necessary for logic operations. The quality of graphene is improved by the shrinkage of the pattern. These results indicate that graphene on silicon using the microfabricated substrate is a promising material for the realization of graphene-based devices.

The domain structure of antiferromagnetic (AFM) NiO(100) has been investigated by nonmagnetic x-ray linear dichroism (XLD) at the O $K$ edge using photoemission electron microscopy and linearly polarized x-ray light. The evolution of XLD image contrast as the function of the angle between the crystal orientation and the incident $s$- or $p$-polarized light is clearly observed. The angular dependence of the XLD contrast is in good agreement with the calculated x-ray absorption cross section of O 1$s$ to 2$p$ orbital that is deformed anisotropically by the strong hybridization with Ni 3$d$ orbitals. This agreement strongly supports the conclusion that the observed XLD contrast reflects the twin-domain ($T$-domain) structure of the NiO crystal. By comparing the experimental data with the calculation, it is possible to assign each domain contrast to a specific $T$-domain in the quantitative manner. The proposed simple and clear way of $T$-domain assignment will be useful for investigating the magnetic domain structures of NiO and other oxide AFM materials such as FeO, CoO, and CuO, and will be important for understanding the magnetic properties of AFM materials, such as the exchange bias effect.

Angle-resolved photoelectron spectroscopy was measured in the Ce 3 d →4 f resonance energy region for the paramagnetic state of CeRu 2 Si 2 , Ce 0.84 La 0.16 Ru 2 Si 2 , and LaRu 2 Si 2 to investigate a variation of band structures around the quantum critical point (QCP). While the results clearly demonstrate the difference of the band structures between CeRu 2 Si 2 and LaRu 2 Si 2 , the observed band structures of CeRu 2 Si 2 and Ce 0.84 La 0.16 Ru 2 Si 2 resemble each other. The results indicate that the Ce 4 f electrons in the paramagnetic state have an itinerant character in either side of the critical composition, and Ce 1- x La x Ru 2 Si 2 near QCP is similar to CeRu 2 (Si 1- x Ge x ) 2 .

Electronic structure of heavily over-doped Bi 1.72 Pb 0.38 Sr 1.88 CuO 6+δ (Bi2201) superconductor was investigated by using the angle-resolved photoemission spectroscopy with soft x-ray as the incident photon source (SX-ARPES), which is known as one of the best bulk sensitive experimental techniques to investigate the electronic structure. By using the Cu 2 p –3 d resonance condition, we succeeded in determining the energy–momentum dispersion near the Fermi level and the Fermi surface. It is clearly shown that both SX- and VUV-ARPES are capable of determining the energy–momentum dispersion near e F at least for the homologous series of Bi 2 Sr 2 Ca n Cu n +1 O 6+2 n +δ cuprate superconductors, and that the combinational use of SX- and VUV-ARPES is one of the best experimental methods to determine the electronic structure of bulk materials.

The band structures of heavy Fermion superconductors UPd2Al3 and UNi2Al3 in paramagnetic phase were studied by soft X-ray angle-resolved photoemission. The results were compared with the results of the band structure calculation treating all U 5f electrons being itinerant. We have found that their overall band structures are described by the calculation. This suggests that U 5f electrons have itinerant nature in these compounds and band structure calculation is a reasonable starting point to model their electronic structure.