Syuta Honda

Chirality control of magnetic vortex in a square Py dot using current-induced Oersted field

We have proposed a method for controlling the vortex chirality in a squared permalloy dot by using the circular Oersted field locally induced by flowing a DC current across a small Py/Cu junctions. The reliability of the chirality control has been evaluated by measuring the nonlocal spin valve signal. The desired vortex chirality has been obtained when the injecting DC current has a moderate magnitude. However, the large DC current is found to reduce the control reliability. Another possibility for controlling the vortex structure using the large DC current injection was also discussed.

Spin polarization control through resonant states in an Fe/GaAs Schottky barrier

Spin polarization of the tunnel conductivity has been studied for Fe/GaAs junctions with Schottky barriers. It is shown that band matching of resonant interface states within the Schottky barrier defines the sign of spin polarization of electrons transported through the barrier. The results account very well for experimental results including the tunneling of photoexcited electrons and suggest that the spin polarization (from

Potential variations around grain boundaries in impurity-doped BaSi2 epitaxial films evaluated by Kelvin probe force microscopy

\ensuremath{-}100%

Bias dependence of spin-polarized tunnel current through Fe/GaAs and Fe/GaAs/Fe junctions

to 100%) is dependent on the Schottky barrier height. They also suggest that the sign of the spin polarization can be controlled with a bias voltage.

Electronic structures and magnetic moments of Co3FeN thin films grown by molecular beam epitaxy

Potential variations around the grain boundaries (GBs) in antimony (Sb)-doped n-type and boron (B)-doped p-type BaSi2 epitaxial films on Si(111) were evaluated by Kelvin probe force microscopy. Sb-doped n-BaSi2 films exhibited positively charged GBs with a downward band bending at the GBs. The average barrier height for holes was approximately 10 meV for an electron concentration n ≈ 1017 cm−3. This downward band bending changed to upward band bending when n was increased to n = 1.8 × 1018 cm−3. In the B-doped p-BaSi2 films, the upward band bending was observed for a hole concentration p ≈ 1018 cm−3. The average barrier height for electrons decreased from approximately 25 to 15 meV when p was increased from p = 2.7 × 1018 to p = 4.0 × 1018 cm−3. These results are explained under the assumption that the position of the Fermi level Ef at GBs depends on the degree of occupancy of defect states at the GBs, while Ef approached the bottom of the conduction band or the top of the valence band in the BaSi2 grain ...

First-principles study of energy band gap of single-layer Mo1−xCrxS2

Spin polarization of the tunnel current under finite bias voltage is studied theoretically for Fe/GaAs junctions with Schottky barriers and Fe/GaAs/Fe tunnel junctions, using a realistic tight-binding model and linear response theory. Calculating the spin polarization of the tunnel current across the interface as a function of bias voltage, we show that the spin-polarized interface resonant states within the Schottky barrier significantly influence spin-dependent tunnelling. The position of the resonant states depends on the Schottky barrier height, and the spin polarization of the tunnel current can be negative for a rather wide range of bias voltage, depending on the Schottky barrier height. The magnetoresistance of Fe/GaAs/Fe tunnel junctions is also negative under high bias voltage, because of the interfacial resonant states in the GaAs layer. The present results demonstrate the importance of controlling Schottky barrier formation to obtain high spin polarization in Fe/GaAs junctions.

Current-induced dynamics of bubble domains in perpendicularly magnetized TbFeCo wires

We evaluated electronic structures and magnetic moments in Co3FeN epitaxial films on SrTiO3(001). The experimentally obtained hard x-ray photoemission spectra of the Co3FeN film have a good agreement with those calculated. Site averaged spin magnetic moments deduced by x-ray magnetic circular dichroism were 1.52 μB per Co atom and 2.08 μB per Fe atom at 100 K. They are close to those of Co4N and Fe4N, respectively, implying that the Co and Fe atoms randomly occupy the corner and face-centered sites in the Co3FeN unit cell.

Correlation Effects of Localized Impurities on Electron Transport under 1-D Nano-Structures

The electronic structures of single-layer Mo1−xCrxS2 are calculated by the spin-polarized density functional method. Single-layer Mo1−xCrxS2 exhibits a direct band gap for any Cr concentration (x). The energy band gap monotonically decreases as a function of x and takes an ideal value for photovoltaic applications at x 0.23.

Fabrication of L-shaped Fe4N ferromagnetic narrow wires and position control of magnetic domain wall with magnetic field

We investigated the bubble-domain dynamics in TbFeCo wires with perpendicular magnetization under electric current flows. In TbFeCo wires with relatively low saturation magnetization (Ms), the current pulse caused the bubble domains to collapse without moving. In TbFeCo wires with relatively high Ms, however, the bubble domains grew in the current direction. We explain these shape changes by assessing the Ms-dependent forces caused by the exchange field and magnetostatic field. We also found that we could control the current-induced behaviors of the bubble domains by using an external magnetic field.

Magnetization and spin-polarized conductance of asymmetrically hydrogenated graphene nanoribbons: significance of sigma bands

We investigate the spatial correlation effects of ionized impurities on electron transport properties under quasi-1D nanowire structures. The impurity-limited resistance is evaluated with the Landauer formula under various spatial distributions of impurities and the simulation results are theoretically analyzed. We show that phase interference is significant even at room temperature when the separation between impurities along the axis direction is small, whereas strong phase randomization takes place as the separation increases.