arXiv subjects

K. Uchida

Publications and source records attributed to K. Uchida.

41 records · Page 3Linked to original sources

arXiv2011

Acoustic spin pumping: Direct generation of spin currents from sound waves in Pt/Y3Fe5O12 hybrid structures

Using a Pt/Y3Fe5O12 (YIG) hybrid structure attached to a piezoelectric actuator, we demonstrate the generation of spin currents from sound waves. This "acoustic spin pumping" (ASP) is caused by the sound wave generated by the piezoelectric actuator, which then modulates the distribution function of magnons in the YIG layer and results in a pure-spin-current injection into the Pt layer across the Pt/YIG interface. In the Pt layer, this injected spin current is converted into an electric voltage due to the inverse spin-Hall effect (ISHE). The ISHE voltage induced by the ASP is detected by measuring voltage in the Pt layer at the piezoelectric resonance frequency of the actuator coupled with the Pt/YIG system. The frequency-dependent measurements enable us to separate the ASP-induced signals from extrinsic heating effects. Our model calculation based on the linear response theory provides us with a qualitative and quantitative understanding of the ASP in the Pt/YIG system.

cond-mat.mtrl-sci↗

arXiv2010

Spin Seebeck insulator

Thermoelectric generation is an essential function of future energy-saving technologies. However, this generation has been an exclusive feature of electric conductors, a situation which inflicts a heavy toll on its application; a conduction electron often becomes a nuisance in thermal design of devices. Here we report electric-voltage generation from heat flowing in an insulator. We reveal that, despite the absence of conduction electrons, a magnetic insulator LaY2Fe5O12 converts a heat flow into spin voltage. Attached Pt films transform this spin voltage into electric voltage by the inverse spin Hall effect. The experimental results require us to introduce thermally activated interface spin exchange between LaY2Fe5O12 and Pt. Our findings extend the range of potential materials for thermoelectric applications and provide a crucial piece of information for understanding the physics of the spin Seebeck effect.

cond-mat.mtrl-sci↗

arXiv2004

Mid-Infrared Spectra of Dust Debris Around Main-Sequence Stars

We report spectra obtained with the Spitzer Space Telescope in the wavelength range between 14 microns and 35 microns of 19 nearby main-sequence stars with infrared excesses. The six stars with strong dust emission show no recognizable spectral features, suggesting that the bulk of the emitting particles have diameters larger than 10 microns. If the observed dust results from collisional grinding of larger solids, we infer minimum masses of the parent body population between 0.004 of the Earth's mass and 0.06 of the Earth's mass. We estimate grain production rates of 10 Gg/s around lambda Boo and HR 1570; selective accretion of this matter may help explain their peculiar surface abundances. There appear to be inner truncations in the dust clouds at 48 AU, 11 AU, 52 AU and 54 AU around HR 333, HR 506, HR 1082 and HR 3927, respectively.

astro-ph↗

arXiv2000

IRS: the Infrared Spectrograph on SIRTF

astro-ph↗

arXiv1999

Extragalactic Spectroscopy with SIRTF/IRS

The Infrared Spectrograph (IRS) is one of the three instruments on board the Space Infrared Telescope Facility (SIRTF) to be launched in December 2001. The IRS will provide high resolution spectra (R = 600) from 10-37 microns and low resolution spectra (R >= 60) from 5-40microns. Its high sensitivity and ``spectral mapping''-mode make it a powerful instrument for observing both faint point-like and extended sources. We discuss the performance of the IRS on faint extragalactic targets and present simulated spectra of starbursts and AGNs at high redshift. In addition, we discuss the determination of redshifts from the low resolution spectra.

astro-ph↗