262 research outputs found
Photoinduced magnetic bound state in itinerant correlated electron system with spin-state degree of freedom
Photo-excited state in correlated electron system with spin-state degree of
freedom is studied. We start from the two-orbital extended Hubbard model where
energy difference between the two orbitals is introduced. Photo-excited
metastable state is examined based on the effective model Hamiltonian derived
by the two-orbital Hubbard model. Spin-state change is induced by
photo-irradiation in the low-spin band insulator near the phase boundary.
High-spin state is stabilized by creating a ferromagnetic bound state with
photo-doped hole carriers. An optical absorption occurs between the bonding and
antibonding orbitals inside of the bound state. Time-evolution for
photo-excited states is simulated in the time-dependent mean-field scheme.
Pair-annihilations of the photo-doped electron and hole generate the high-spin
state in a low-spin band insulator. We propose that this process is directly
observed by the time-resolved photoemission experiments.Comment: 15 pages, 16 figure
Continuous Generation of Spinmotive Force in a Patterned Ferromagnetic Film
We study, both experimentally and theoretically, the generation of a dc
spinmotive force. By exciting a ferromagnetic resonance of a comb-shaped
ferromagnetic thin film, a continuous spinmotive force is generated.
Experimental results are well reproduced by theoretical calculations, offering
a quantitative and microscopic understanding of this spinmotive force.Comment: 4 pages, 4 figures, accepted to Physical Review Letter
証券化および担保制約下の信念の違いによるバブルについて
学位の種別: 課程博士審査委員会委員 : (主査)東京大学教授 松島 斉, 東京大学教授 柳川 範之, 東京大学准教授 青木 浩介, 東京大学准教授 尾山 大輔, 東京大学講師 平野 智裕University of Tokyo(東京大学
Equation-of-motion approach of spin-motive force
We formulate a quantitative theory of an electromotive force of spin origin,
i.e., spin-motive force, by the equation-of-motion approach. In a ferromagnetic
metal, electrons couple to the local magnetization via the exchange
interaction. Electrons feel spin dependent forces due to this interaction, and
then the spin-motive force and the anomalous Hall effect appears. We have
revealed that the origin of these phenomena is a misalignment between the
conduction electron spin and the local magnetization.Comment: 3 pages, 3 figure
Linear-response theory of spin Seebeck effect in ferromagnetic insulators
We formulate a linear response theory of the spin Seebeck effect, i.e., a
spin voltage generation from heat current flowing in a ferromagnet. Our
approach focuses on the collective magnetic excitation of spins, i.e., magnons.
We show that the linear-response formulation provides us with a qualitative as
well as quantitative understanding of the spin Seebeck effect observed in a
prototypical magnet, yttrium iron garnet.Comment: 6 pages, 3 figures. Added references and revised argument on the
length scales at the end of Sec.
Dysregulation of erythropoiesis and altered erythroblastic NMDA receptor-mediated calcium influx in Lrfn2-deficient mice
LRFN2 encodes a synaptic adhesion-like molecule that physically interacts with N-methyl-D-aspartate (NMDA) receptor 1 and its scaffold proteins. Previous studies in humans and mice have demonstrated its genetic association with neurodevelopmental disorders such as learning deficiency and autism. In this study, we showed that Lrfn2-deficient (KO) mice exhibit abnormalities of erythropoietic systems due to altered NMDA receptor function. In mature Lrfn2 KO male mice, peripheral blood tests showed multilineage abnormalities, including normocytic erythrocythemia, and reduced platelet volume. Colony forming unit assay using bone marrow cells revealed decreases in the counts of erythrocyte progenitors (CFU-E) as well as granulocytes and monocyte progenitors (CFU-GM). Whole bone marrow cell staining showed that serum erythropoietin (EPO) level was decreased and EPO receptor-like immunoreactivity was increased. Flow cytometry analysis of bone marrow cells revealed increased early erythroblast count and increased transferrin receptor expression in late erythroblasts. Further, we found that late erythroblasts in Lrfn2 KO exhibited defective NMDA receptor-mediated calcium influx, which was inhibited by the NMDA receptor antagonist MK801. These results indicate that Lrfn2 has biphasic roles in hematopoiesis and is associated with the functional integrity of NMDA receptors in hematopoietic cells. Furthermore, taken together with previous studies that showed the involvement of NMDA receptors in hematopoiesis, the results of this study indicate that Lrfn2 may regulate erythropoiesis through its regulatory activity on NMDA receptors
On-The-Fly Observing System of the Nobeyama 45-m and ASTE 10-m Telescopes
We have developed spectral line On-The-Fly (OTF) observing mode for the
Nobeyama Radio Observatory 45-m and the Atacama Submillimeter Telescope
Experiment 10-m telescopes. Sets of digital autocorrelation spectrometers are
available for OTF with heterodyne receivers mounted on the telescopes,
including the focal-plane 5 x 5 array receiver, BEARS, on the 45-m. During OTF
observations, the antenna is continuously driven to cover the mapped region
rapidly, resulting in high observing efficiency and accuracy. Pointing of the
antenna and readouts from the spectrometer are recorded as fast as 0.1 second.
In this paper we report improvements made on software and instruments,
requirements and optimization of observing parameters, data reduction process,
and verification of the system. It is confirmed that, using optimal parameters,
the OTF is about twice as efficient as conventional position-switch observing
method.Comment: 11 pages, 13 figures, accepted for publication in PAS
Spinmotive Force due to Intrinsic Energy of Ferromagnetic Nanowires
We study, both analytically and numerically, a spinmotive force arising from
inherent magnetic energy of a domain wall in a wedged ferromagnetic nanowire.
In a spatially-nonuniform nanowire, domain walls are subjected to an effective
magnetic field, resulting in spontaneous motion of the walls. The spinmotive
force mechanism converts the ferromagnetic exchange and demagnetizing energy of
the nanowire into the electrical energy of the conduction electrons through the
domain wall motion. The calculations show that this spinmotive force can be
several microvolts, which is easily detectable by experiments.Comment: 4 pages, 2 figure
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