arXiv subjects

Eiji Shikoh

Publications and source records attributed to Eiji Shikoh.

24 records · Page 2Linked to original sources

arXiv2013

Spin-pumping-induced spin transport in p-type Si at room temperature

A spin battery concept is applied for the dynamical generation of pure spin current and spin transport in p-type silicon (p-Si). Ferromagnetic resonance and effective s-d coupling in Ni80Fe20 results in spin accumulation at the Ni80Fe20/p-Si interface, inducing spin injection and the generation of spin current in the p-Si. The pure spin current is converted to a charge current by the inverse spin Hall effect of Pd evaporated onto the p-Si. This approach demonstrates the generation and transport of pure spin current in p-Si at room temperature.

cond-mat.mtrl-sci↗

arXiv2013

Dynamical Spin Injection into p-type Germanium at Room Temperature

We demonstrate dynamical spin injection into p-type germanium (Ge) at room temperature (RT) using spin pumping. The generated pure spin current is converted to a charge current by the inverse spin-Hall effect (ISHE) arising in the p-type Ge sample. A clear electromotive force due to the ISHE is detected at RT. The spin-Hall angle for p-type Ge is estimated to be θSHE = 2.6x10-3 at RT, which is much larger than that for p-type Si.

cond-mat.mtrl-sci↗

arXiv2012

An investigation of the inverted Hanle effect in highly-doped Si

The underlying physics of the inverted Hanle effect appearing in Si was experimentally investigated using a Si spin valve, where spin transport was realized up to room temperature. No inverted-Hanle-related signal was observed in a non-local 4-terminal scheme even the same ferromagnetic electrode was used, whereas the signal was detected in a non-local 3-terminal scheme. Although the origin of the inverted Hanle effect has been thought to be ascribed to interfacial roughness beneath a ferromagnetic electrode, our finding is inconsistent with the conventional interpretation. More importantly, we report that there were two different Hanle signals in a non-local 3-terminal scheme, one of which corresponds to the inverted Hanle signal but the other is ascribed to spin transport. These results strongly suggest that (1) there is room for discussion concerning the origin of the inverted Hanle effect, and (2) achievement of spin transport in a non-local 4-terminal scheme is indispensable for further understanding of spin injection, spin transport and spin coherence in Si. Our new findings provide a new and strong platform for arising discussion of the physical essence of Hanle-related spin phenomena.

cond-mat.mtrl-sci↗

arXiv2012

Observation of Huge Magnetoresistance and Multiferroic-like Behavior of Co Nanoparticles in a C60 matrix

Tunneling magnetoresistance (TMR) via oxides or molecules includes fruitful physics, such as spin filtering and hybridized interface states, in addition to various practical applications using large TMR ratio at room temperature. Then, a larger TMR effect with a new fundamental physics is awaited because further progress on spintronics can be realized. Here we report a discovery of a gigantic TMR ratio of 1,400,000% in a C60-Co nanocomposite spin device. The observed effect is induced by a combination of a Coulomb blockade effect and a novel magnetic switching effect. Theoretical investigation reveals that an electric field and a magnetic field control the magnetization and the electronic charging state, respectively, of the Co nanoparticles as in physics of multiferroicity.

cond-mat.mtrl-sci↗

arXiv2011

The effect of spin drift on spin accumulation voltages in highly-doped Si

An investigation was carried out into the effect of spin drift on spin accumulation signals in highly-doped Si using non-local 4-terminal (NL-4T) and 3-terminal (NL-3T) methods. The spin signals in the NL-4T scheme were not affected by spin drift, and the bias dependence was governed by whether spins were injected into or extracted from the Si channel. In contrast, the spin signal was strongly modulated by the bias electric field in the NL-3T scheme. The bias electric field dependence of the spin signals in the NL-3T method was quantitatively clarified using the spin drift-diffusion equation, and the results can be reasonably explained.

cond-mat.mtrl-sci↗

arXiv2011

Experimental Investigation of Spin Transport Properties in Silicon by Using a Non-local Geometry

A systematic investigation of spin transport properties in silicon at 8 K by using a non-local geometry is presented. The spin injection signal in the non-local scheme is found to increase in proportion to the evolution of bias electric currents. Theoretical fittings using the Hanle-type spin precession signals reveal that the spin polarization of the transported spin in the Si is much less affected by the change in the bias electric current compared with a case of the other spin devices, which induces a unique bias dependence of the spin signals.

cond-mat.mtrl-sci↗