Masaaki Tanaka

We have observed very large tunneling magnetoresistance (TMR) in epitaxially grown ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}/\mathrm{AlAs}/{\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}$ ferromagnetic semiconductor tunnel junctions. Large TMR ratios more than $70%$ (maximum $75%$) were obtained in junctions with a very thin ( $\ensuremath{\le}1.6\mathrm{nm}$) AlAs tunnel barrier when the magnetic field was applied along the $[100]$ axis in the film plane. The TM

We have successfully grown ferromagnetic MnGa ultrathin films on GaAs substrates by molecular beam epitaxy. Reflection high energy electron diffraction and cross-sectional transmission electron microscopy show that monocrystalline MnGa films are grown with the c axis of the tetragonal unit cell normal to the (001) GaAs substrates. Both magnetization measurements by vibrating sample magnetometer and extraordinary Hall effect (EHE) measurements indicate perpendicular magnetization, with the remnan

We have studied template effects in molecular beam epitaxy (MBE) of ferromagnetic MnAs thin films on (001) GaAs substrates. When As2 flux was first supplied without Mn flux on the (001) GaAs prior to the MnAs growth, the surface reconstruction was disordered c(4×4), a more As-rich surface than c(4×4). The growth direction of the MnAs thin film grown on this surface is [1̄100] and the easy magnetization axis was found to be along the [1̄1̄20] of MnAs and the [110] of GaAs. In contrast, when one m

We have successfully grown single-crystalline ferromagnetic MnAs thin films on (001) GaAs substrates by molecular beam epitaxy. By reflection high energy electron diffraction and x-ray measurements, the growth direction of the MnAs thin films was found to be [100] on (001) GaAs, and the epitaxial relationship was [0001] MnAs //[10] GaAs and [110] MnAs // [110] GaAs. Magnetization measurements at room temperature have revealed that the epitaxial MnAs thin films have strong magnetic anisotropy, an

Different types of mental fatigue produced different kinds of alterations of the spontaneous EEG variables. Our findings provide new perspectives on the neural mechanisms underlying mental fatigue.

Ferromagnet/semiconductor hybrid structures are attractive and promising as artificial materials for 'semiconductor spintronics', because they can possess magnetic and/or spin-related functions and they have excellent compatibility with semiconductor device structures. We review our studies on the molecular beam epitaxy (MBE) growth of ferromagnet (MnAs)/III–V semiconductor layered heterostructures and nanoscale granular structures, and their magnetic, magneto-transport and magneto-optical prope

This study demonstrates that living with a human-type communication robot may be effective for improving cognitive functions in elderly women living alone.

We have studied structural and magnetic properties of epitaxial MnAs thin films with various thicknesses (L=1.0–200 nm) on GaAs substrates. The MnAs thin films were grown at 200–250 °C on an As-rich disordered c(4×4) (001) GaAs surface by molecular-beam epitaxy (MBE). The growth direction of the MnAs was found to be along the [1̄100] axis of the hexagonal unit cell. X-ray spectra of the MnAs at room temperature have two peaks, indicating that the present MBE-grown MnAs films consist of the hexag

Spin-based electronics or spintronics is an emerging field, in which we try to utilize spin degrees of freedom as well as charge transport in materials and devices. While metal-based spin-devices, such as magnetic-field sensors and magnetoresistive random access memory using giant magnetoresistance and tunneling magnetoresistance, are already put to practical use, semiconductor-based spintronics has greater potential for expansion because of good compatibility with existing semiconductor technol