Search

In this paper, using first-principles calculations based on density-functional theory, the electronic structures, magnetic properties, and half-metallicity in the bulk and (001) surface of quaternary Heusler alloy CoNbMnSi are studied. For the bulk, the CoNbMnSi compound shows half-metallicity with a band gap of 0.5 eV in the down-spin direction at a equilibrium lattice constant of 5.88 Ǻ. At a similar equilibrium lattice constant, the half-metallicity confirmed in the bulk CoNbMnSi, is ruined at both NbSi- and MnCo-terminated (001) surfaces and subsurfaces. Based on the magnetic property calculations, the magnetic moments of Mn and Nb atoms at the (001) surfaces increase with respect to the corresponding bulk values, while the magnetic moment of Co and Si atoms decreases. The spin-polarization ratio clearly decreases below 75% for (001) surfaces and subsurfaces of the CoNbMnSi alloy. [ABSTRACT FROM AUTHOR]

A theoretical study of integral and differential cross sections as well as of spin-polarization effects is reported for elastic electron scattering by zinc atoms at collision energies up to 3 keV. It has been shown that a P -wave shape resonance appears in the low-energy range of the integral cross sections. Its energy is about 0.19 and 0.20 eV, while its width is about 0.309 and 0.356 eV for the j = 3/2 and j = 1/2 total angular momentum of the electron, respectively. The differential cross sections of scattering and the Sherman-functions S (E , θ) are computed by the parameter-free complex optical potential method. The calculated data are in a good overall agreement with the available experimental and theoretical data in the literature. The energy and angular positions have been located for five critical minima in the differential cross sections. The low-energy minimum is located at [6.63 eV; 102.34°], while the high-energy minimum is at [347.53 eV; 124.11°]. Ten points for the scattered electrons' total spin-polarization (S = ± 1) have been found in the vicinity of the critical minima along with the energy and the angular widths of the spin-polarization peaks (where | S | ≥ 0.9). • Fine parameters of elastic electron-atom scattering has very useful technological aspects. • Accurate scattering cross sections are necessary, but still missing for some atomic target species. • We propose a new set of electron-impact cross sections for zinc atom in a broad collision energy range (from 0.01 up to 3000 eV). • Spin polarization parameters and Sherman functions are also calculated. [ABSTRACT FROM AUTHOR]

We have investigated the electronic states and spin polarization of half-metallic ferromagnet CrO 2 (100) epitaxial films by bulk-sensitive spin-resolved photoemission spectroscopy with a focus on non-quasiparticle (NQP) states derived from electron-magnon interactions. We found that the averaged values of the spin polarization are approximately 100% and 40% at 40 K and 300 K, respectively. This is consistent with the previously reported result [H. Fujiwara et al., Appl. Phys. Lett. 106 , 202404 (2015).]. At 100 K, peculiar spin depolarization was observed at the Fermi level ( E F ), which is supported by theoretical calculations predicting NQP states. This suggests the possible appearance of NQP states in CrO 2 . We also compare the temperature dependence of our spin polarizations with that of the magnetization. [ABSTRACT FROM AUTHOR]

A novel design of high-voltage compatible polarimeter for spin-resolved hard X-ray photoelectron spectroscopy (Spin-HAXPES) went into operation at beamline BL09XU of SPring-8 in Hyogo, Japan. The detector is based on the well-established principle of electron diffraction from a W(001) single-crystal at a scattering energy of 103.5 eV. It's special feature is that it can be operated at a high negative bias potential up to 10 kV, necessary to access the HAXPES range. The polarimeter is operated behind a large hemispherical analyzer (Scienta R-4000). It was optimized for high transmission of the transfer optics. A delay-line detector (20 mm dia.) is positioned at the exit plane of the analyzer enabling conventional multichannel intensity spectroscopy simultaneously with single-channel spin analysis. The performance of the combined setup is demonstrated by the spin-resolved data for the valence-region of a FeCo functional layer of a tunneling device, buried beneath 3 nm of oxidic material. The well-structured spin polarization spectrum validates Spin-HAXPES in the valence energy range as powerful method for bulk electronic structure analysis. The spin polarization spectrum exhibits a rich structure, originating from clearly discernible transitions in the majority and minority partial spin spectra. [ABSTRACT FROM AUTHOR]

The polarization vector P of scattered electrons interacting with a polarized target electrons is compared with the entanglement (or non-separability) of the electron states of the interacting electron pair. The separability S is defined as a linear function of the von Neumann entropy. The shapes of the functions P ( θ , Ω , φ ) and S ( θ , Ω , φ ) are similar and simultaneously achieve their maximum value at the scattering angle θ values close to 0 and π and simultaneously tend to zero in the case of symmetric scattering at θ ≈ π /2. In the latter case the scattered electrons are described by an asymmetric spin part of the wave function, which by definition corresponds to the spin entangled ( S ≈ 0) electron states of the interacting electron pair. Comparison of the model calculation results with experimental results of the spin polarized electron spectroscopy of the ferromagnetic solid shows qualitative agreement. The analytical expression relating polarization and separability of the two interacting particles enables use the measured polarization of scattered electrons for estimation of the spin-entanglement or separability of the two particle systems. [ABSTRACT FROM AUTHOR]

The geometric symmetry of the surface plays an important role for the spin–orbit-induced spin texture of two-dimensional electronic states. This article reviews the peculiar Rashba spins induced by a C 3 symmetry, including the completely spin polarized surface states with the polarization vector oriented perpendicular to the surface, i.e. a direction that is not expected in a typical Rashba system. This review also describes that this peculiar Rashba situation has possibility to suppress backscattering and therefore to greatly improve the efficiency of spin transport, which is an essential issue in the development of high-performance semiconductor spintronic devices. [ABSTRACT FROM AUTHOR]

The surface of W(1 1 0) exhibits a flattened Dirac-cone-like surface state S 1 with a remarkable spin texture within a spin–orbit-induced symmetry gap. Along Γ S ¯ , S 1 hybridizes spin-selectively with an almost spin-degenerate surface state S 2 . Beyond the spin-selective hybridization point, the surface state S 2 exhibits a spin splitting with a change of the spin polarization at the band bottom. For normal electron emission, S 1 shows spin-dependent intensities depending on the experimental geometry. This behavior is understood as a consequence of a mixed Σ 1 and Σ 3 symmetry of the state. This finding opens a new pathway to studies of the orbital symmetry of electronic states in solids with spin–orbit interaction, without the need of polarization-dependent ARPES. [ABSTRACT FROM AUTHOR]

We report high-resolution spin- and angle-resolved photoemission spectroscopy of bismuth thin film on Si(1 1 1) to discuss the spin structure of surface states. We found that, unlike conventional picture of the Rashba splitting, the magnitude of the in-plane spin polarization is asymmetric between two hole pockets across the Brillouin-zone center. In addition, these pockets exhibit a giant out-of-plane spin polarization as large as the in-plane counterpart, which changes the sign across the Γ ¯     M ¯ line. We also revealed that the spin polarization of the Rashba surface states near the Brillouin-zone boundary (the M ¯ point) is gradually reduced on decreasing the film thickness. Our result provides a new pathway to generate and control spin-polarized electrons in the Rashba system. [ABSTRACT FROM AUTHOR]

We describe the principle, the preparation, and the calibration of a spin-polarizing electron mirror in multichannel spin polarimetry. We show data obtained by two independent devices (a goniometer-type LEED set-up and a momentum-microscope set-up) and compare them to the results of a relativistic multiple scattering theory. We also discuss the effects of misalignment and mosaic structure of the crystal. For multi-channel detection we find a 5000-fold increase of efficiency over a single-channel spin-detector. The lifetime of the detector is more than 6 months in ultra-high vacuum. [ABSTRACT FROM AUTHOR]

• The energy and the HM gaps were calculated as 0.57 and 0.12 eV. • The HM is preserved at the Sc1 and Ge-terminated (111) surfaces. • The adhesion energy shows that the Sc1-Sb shape is more stable than the others. Our study showed that full-Heusler Sc 2 CrGe displays half metallic ferromagnetism with an energy gap of 0.57 eV and a spin-flip gap of 0.12 eV in the majority spin channel at an optimization equilibrium lattice constant of 6.5 Å. In this study, we investigate extensively the electronic and magnetic features of the (111), (001), and (110) surfaces and the interface with the semiconductor InSb (111) via applying the first-principles computations of the density functional theory. The atomic density of states confirms that the half-metallicity discovered in the bulk Sc 2 CrGe is kept at the Sc(2)Ge-terminated (001), Sc(1)-, and Ge-terminated (111) surfaces, but it is lost at the Sc(2)- and Cr-terminated (111), Sc(1)Cr- terminated (001), and Sc 2 CrGe (110) surfaces. For the Sc 2 CrGe/InSb (111) interface, the bulk half-metallicity is destroyed at the Sc(1)-In, Sc(1)-Sb, and Ge-In configurations while the Ge-Sb configuration exhibits a full spin polarization. Moreover, the computed interfacial adhesion energy shows that the Sc(1)-Sb shape is more stable than the others. The calculated magnetic moments of interface atoms (Sc and Ge) decrease compared to the corresponding bulk values. [ABSTRACT FROM AUTHOR]

• We propose the Right-angle-deflection Imaging Analyzer (RADIAN). • RADIAN can be suitably used for measuring wide 2D angular distribution. • RADIAN basic properties are evaluated in comparison to CHA properties. • RADIAN has three times the acceptance cone angle of CHA. • RADIAN is the only analyzer that enables perpendicular spin texture imaging. A 90°-deflection imaging electron analyzer for measuring wide 2D angular distribution and perpendicular spin texture is proposed. This analyzer, which we call "right-angle-deflection imaging analyzer (RADIAN)", provides electrostatic 90°-deflection and 2D focusing of an electron beam. Here a large acceptance angle comparable to that of cylindrical mirror analyzer (CMA) is achieved without using a grid, while CMA uses grids at the entrance and the exit of an electrostatic field. The 90° deflection allows measuring spin polarization not only in the in-plane direction, but also in the surface-normal direction. Basic properties of RADIAN, calculated by ray tracing, are shown in comparison with those of the most widely used electron energy analyzer, i.e., concentric hemispherical analyzer (CHA). RADIAN has a much higher 2D focusing capability than CHA and allows a much larger acceptance angle for 2D imaging. Moreover, the high focusing capability of RADIAN allows us to obtain high energy resolution comparable to that obtained in CHA. A simple and effective way to achieve higher energy resolution is to combine two or more RADIANs in tandem. Double-pass and triple-pass analyzers in this combination are taken into account. For a practical application, we consider a combination of RADIAN with the recently proposed ±90° omnidirectional photoelectron acceptance lens. RADIAN can be suitably used to develop a wide-angle 2D imaging analyzer, and can also be used to develop a spin-resolved 2D imaging analyzer that can perform perpendicular-spin-texture imaging. [ABSTRACT FROM AUTHOR]

• We report on the growth and characterization of Fe/Co bilayers on bcc W(110). • The bottom Co layer relaxes to its bulk hcp structure showing an hexagonal surface. • Even with the Co layer, we detect Fe relaxation with the formation of bcc nuclei. • We measure a not nil in-plane spectral spin polarization at magnetic remanence. We report on the growth of a Fe/Co bilayer on W(110) and its electronic and magnetic structure characterization by means of low energy electron diffraction and spin-resolved photoemission spectroscopies. The Co bottom layer, investigated in the thickness range from 2 to 10 monolayers (ML), relaxes immediately to its bulk hcp structure and is therefore used to provide an hexagonal top surface for the growth of metastable Fe films. Notwithstanding the presence of the Co layer, and similar to our previous findings concerning the growth of Fe on a Ni layer [Phys Rev B 94 195155], we report the formation of bcc nuclei, indicative of lattice relaxation, even for a Fe thicknesses as low as 2 ML. For all the Fe/Co thickness combinations and at magnetic remanence, we were able to measure a not nil in-plane spectral spin polarization. [ABSTRACT FROM AUTHOR]

Vanadium diselenide (VSe 2) is a van der Waals layered transitional metal dichalcogenide, which has attracted intensive attention due to the coexistence of charge density wave (CDW) transition and magnetic property down to two-dimension limit. We apply Spin- and angle-resolved photoemission spectroscopy measurement to explore the evolution of the valence eletronic states of VSe 2 accompanied with the CDW transition. The V 3 d -derived-band in the vicinity of Fermi energy shows negligible spin polarization both below and above the CDW transition temperature. Furthermore, a sizable spin polarization of Se 4 p electronic states has been clearly observed, indicating an atomic-layer-dependent spin polarization in VSe 2. Our results provide new clues to understand the spin polarized electronic states in transitional metal dichalcogenides. [ABSTRACT FROM AUTHOR]