52 research outputs found
Spin Drift in Highly Doped n-type Si
A quantitative estimation of spin drift velocity in highly doped n-type
silicon (Si) at 8 K is presented in this letter. A local two-terminal Hanle
measurement enables the detection of a modulation of spin signals from the Si
as a function of an external electric field, and this modulation is analyzed by
using a spin drift-diffusion equation and an analytical solution of the
Hanle-type spin precession. The analyses reveal that the spin drift velocity is
linearly proportional to the electric field. The contribution of the spin drift
effect to the spin signals is crosschecked by introducing a modified nonlocal
four-terminal method.Comment: 16 pages, 3 figure
Room-Temperature Electron Spin Transport in a Highly Doped Si Channel
We report on the first demonstration of generating a spin current and spin
transport in a highly doped Si channel at room temperature (RT) using a
four-terminal lateral device with a spin injector and a detector consisting of
an Fe/MgO tunnel barrier. Spin current was generated using a nonlocal
technique, and spin injection signals and Hanle-type spin precession were
successfully detected at 300 K, thus proving spin injection with the
elimination of spurious signals. The spin diffusion length and its lifetime at
RT were estimated to be 0.6 \"im and 1.3 ns by the Hanle-type spin precession,
respectively.Comment: 14 pages, 4 Figure
A novel inhibitory mechanism of MRTF-A/B on the ICAM-1 gene expression in vascular endothelial cells
The roles of myocardin-related transcription factor A (MRTF-A) and MRTF-B in vascular endothelial cells are not completely understood. Here, we found a novel regulatory mechanism for MRTF-A/B function. MRTF-A/B tend to accumulate in the nucleus in arterial endothelial cells in vivo and human aortic endothelial cells (HAoECs) in vitro. In HAoECs, nuclear localization of MRTF-A/B was not significantly affected by Y27632 or latrunculin B, primarily due to the reduced binding of MRTF-A/B to G-actin and in part, to the low level of MRTF-A phosphorylation by ERK. MRTF-A/B downregulation by serum depletion or transfection of siRNA against MRTF-A and/or MRTF-B induced ICAM-1 expression in HAoECs. It is known that nuclear import of nuclear factor-kappa B (NF-kappa B) plays a key role in ICAM-1 gene transcription. However, nuclear accumulation of NF-kappa B p65 was not observed in MRTF-A/B-depleted HAoECs. Our present findings suggest that MRTF-A/B inhibit ICAM-1 mRNA expression by forming a complex with NF-kappa B p65 in the nucleus. Conversely, downregulation of MRTF-A/B alleviates this negative regulation without further translocation of NF-kappa B p65 into the nucleus. These results reveal the novel roles of MRTF-A/B in the homeostasis of vascular endothelium
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.Comment: 14 pages, 3 figure
Elastic properties of the Non-Fermi liquid metal and the Dense Kondo semiconductor
We have investigated the elastic properties of the Ce-based filled
skutterudite antimonides CeRuSb and CeOsSb by means
of ultrasonic measurements. CeRuSb shows a slight increase around
130 K in the temperature dependence of the elastic constants ,
(-)/2 and . No apparent softening toward low
temperature due to a quadrupolar response of the 4-electronic ground state
of the Ce ion was observed at low temperatures. In contrast CeOsSb
shows a pronounced elastic softening toward low temperature in the longitudinal
as a function of temperature () below about 15 K, while a slight
elastic softening was observed in the transverse below about 1.5 K.
Furthermore, CeOsSb shows a steep decrease around a phase
transition temperature of 0.9 K in both and. The elastic
softening observed in below about 15 K cannot be explained
reasonably only by the crystalline electric field effect. It is most likely to
be responsible for the coupling between the elastic strain and the
quasiparticle band with a small energy gap in the vicinity of Fermi level. The
elastic properties and the 4 ground state of Ce ions in CeRuSb
and CeOsSb are discussed from the viewpoint of the crystalline
electric field effect and the band structure in the vicinity of Fermi level.Comment: 9 pages, 11 figures, regular pape
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.Comment: 16 pages, 3 figures (To appear in Physical Review B (Rapid
Communications)
Electrical Spin Injection into Silicon using MgO Tunnel Barrier
We observed spin injection into silicon through Fe/MgO tunnel barrier by
using non-local magnetoresistance measurement technique. Fe/MgO tunnel barrier
contacts with a lateral spin valve structure were fabricated on phosphorous
doped silicon-on-insulator substrate. Spin injection signals in the non-local
scheme were observed up to 120K, which is the highest value where band
transferred spins in Si have ever been reported, and spin diffusion length was
estimated to be about 2.25um at 8K. Temperature dependence and injection
current dependence of the non-local voltage were also investigated. It is
clarified that MgO tunnel barrier is effective for the spin injection into
silicon.Comment: 15pages, 4 figures. To appear in Applied Physics Expres
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