64 research outputs found
Observation of Magnetic Edge State and Dangling Bond State on Nanographene in Activated Carbon Fibers
The electronic structure of nanographene in pristine and fluorinated
activated carbon fibers (ACFs) have been investigated with near-edge x-ray
absorption fine structure (NEXAFS) and compared with magnetic properties we
reported on previously. In pristine ACFs in which magnetic properties are
governed by non-bonding edge states of the \pi-electron, a pre-peak assigned to
the edge state was observed below the conduction electron {\pi}* peak close to
the Fermi level in NEXAFS. Via the fluorination of the ACFs, an extra peak,
which was assigned to the \sigma-dangling bond state, was observed between the
pre-peak of the edge state and the {\pi}* peak in the NEXAFS profile. The
intensities of the extra peak correlate closely with the spin concentration
created upon fluorination. The combination of the NEXAFS and magnetic
measurement results confirms the coexistence of the magnetic edge states of
\pi-electrons and dangling bond states of \sigma-electrons on fluorinated
nanographene sheets.Comment: 4 figures, to appear in Phys. Rev.
X-ray study of ferroic octupole order producing anomalous Hall effect
放射光でついに見えた磁気オクタポール --熱を電気に変える新たな担い手--. 京都大学プレスリリース. 2021-09-27.Recently found anomalous Hall, Nernst, magnetooptical Kerr, and spin Hall effects in the antiferromagnets Mn₃X (X = Sn, Ge) are attracting much attention for spintronics and energy harvesting. Since these materials are antiferromagnets, the origin of these functionalities is expected to be different from that of conventional ferromagnets. Here, we report the observation of ferroic order of magnetic octupole in Mn₃Sn by X-ray magnetic circular dichroism, which is only predicted theoretically so far. The observed signals are clearly decoupled with the behaviors of uniform magnetization, indicating that the present X-ray magnetic circular dichroism is not arising from the conventional magnetization. We have found that the appearance of this anomalous signal coincides with the time reversal symmetry broken cluster magnetic octupole order. Our study demonstrates that the exotic material functionalities are closely related to the multipole order, which can produce unconventional cross correlation functionalities
Relationship between charge redistribution and ferromagnetism at the heterointerface between perovskite oxides LaNiO3 and LaMnO
To investigate the relationship between the charge redistribution and
ferromagnetism at the heterointerface between perovskite transition-metal
oxides LaNiO (LNO) and LaMnO (LMO), we performed x-ray absorption
spectroscopy and x-ray magnetic circular dichroism (XMCD) measurements. In the
LNO/LMO heterostructures with asymmetric charge redistribution, the electrons
donated from Mn to Ni ions are confined within one monolayer (ML) of LNO at the
interface, whereas holes are distributed over 3-4 ML on the LMO side. A
detailed analysis of the Ni- and Mn- XMCD spectra reveals
that Ni magnetization is induced only by the Ni ions in the 1 ML LNO
adjacent to the interface, while the magnetization of Mn ions is increased in
the 3-4 ML LMO of the interfacial region. The characteristic length scale of
the emergent (increased) interfacial ferromagnetism of the LNO (LMO) layers is
in good agreement with that of the charge distribution across the interface,
indicating a close relationship between the charge redistribution due to the
interfacial charge transfer and the ferromagnetism of the LNO/LMO interface.
Furthermore, the XMCD spectra clearly demonstrate that the vectors of induced
magnetization of both ions are aligned ferromagnetically, suggesting that the
delicate balance between the exchange interactions occurring inside each layer
and across the interface may induce the canted ferromagnetism of Ni
ions, resulting in weak magnetization in the 1 ML LNO adjacent to the
interface.Comment: 22 pages, 4 figure
Interface-induced perpendicular magnetic anisotropy of Co nanoparticles on single-layer h-BN/Pt(111)
Ferromagnetism with perpendicular magnetic anisotropy (PMA) was observed at room temperature in cobalt nanoparticles (NPs) grown on hexagonal boron nitride (h-BN) on a Pt(111) surface. It was shown that the Co NPs have planar hexagonal shapes with a mean diameter of ∼20 nm and a mean height of ∼1.6 nm. The depth-resolved analysis of X-ray magnetic circular dichroism at the Co L2,3-edges revealed that in the ferromagnetic Co NPs, the ratio of the orbital magnetic moment to the spin magnetic moment in the out-of-plane direction becomes larger at the Co NP/h-BN interface than the ratio in bulk Co. The B and N K-edge near edge X-ray absorption fine structures showed the orbital hybridization between the π orbitals of h-BN and d orbitals of Co at the interface, as an origin of the orbital magnetic moment enhancement possibly giving rise to PMA in the Co NPs
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Analysis of the African coelacanth genome sheds light on tetrapod evolution
It was a zoological sensation when a living specimen of the coelacanth was first discovered in 1938, as this lineage of lobe-finned fish was thought to have gone extinct 70 million years ago. The modern coelacanth looks remarkably similar to many of its ancient relatives, and its evolutionary proximity to our own fish ancestors provides a glimpse of the fish that first walked on land. Here we report the genome sequence of the African coelacanth, Latimeria chalumnae. Through a phylogenomic analysis, we conclude that the lungfish, and not the coelacanth, is the closest living relative of tetrapods. Coelacanth protein-coding genes are significantly more slowly evolving than those of tetrapods, unlike other genomic features . Analyses of changes in genes and regulatory elements during the vertebrate adaptation to land highlight genes involved in immunity, nitrogen excretion and the development of fins, tail, ear, eye, brain, and olfaction. Functional assays of enhancers involved in the fin-to-limb transition and in the emergence of extra-embryonic tissues demonstrate the importance of the coelacanth genome as a blueprint for understanding tetrapod evolution
Development of a high-resolution soft x-ray monochromator and its application to the study on surface chemistry and surface magnetism
報告番号: 乙14663 ; 学位授与年月日: 2000-04-10 ; 学位の種別: 論文博士 ; 学位の種類: 博士(理学) ; 学位記番号: 第14663号 ; 研究科・専攻: 理学系研究
Development of a high-resolution soft x-ray monochromator and its application to the study on surface chemistry and surface magnetism
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