2,529 research outputs found
Mechanism of Magnetism in Stacked Nanographite: Theoretical Study
Antiferromagnetism in stacked nanographite is investigated with using the
Hubbard-type model. The A-B stacking is favorable for the hexagonal
nanographite with zigzag edges, in order that magnetism appears. Next, we find
that the open shell electronic structures can be origins of the decreasing
magnetic moment with the decrease of the inter-graphene distance, as
experiments on adsorption of molecules suggest.Comment: 4 pages, 3 figure
Polarization Dependence of Raman Spectra in Strained Graphene
The polarization dependences of the G, D, and 2D (G) bands in Raman
spectra at graphene bulk and edge are examined theoretically. The 2D and D
bands have different selection rules at bulk and edge. At bulk, the 2D band
intensity is maximum when the polarization of the scattered light is parallel
to that of incident light, whereas the D band intensity does not have a
polarization dependence. At edge, the 2D and D bands exhibit a selection rule
similar to that of the G band proposed in a previous paper. We suggest that a
constraint equation on the axial velocity caused by the graphene edge is
essential for the dependence of the G band on the crystallographic orientation
observed in the bulk of strained graphene. This is indicative of that the
pseudospin and valleyspin in the bulk of graphene can not be completely free
from the effect of surrounding edge. The status of the experiments on the G and
D bands at the graphene edge is mentioned.Comment: 11 pages, 3 figure
Formability evaluation of double layer circular tube as a device with energy absorption capacity
Recently, earthquakes frequently occur in Japan. It is desired to promote seismic isolation technology of building. It has been found that newly designed composite material filled with low rigidity material to high rigidity material has significant energy absorbing capacity. However, it must have higher energy absorption capacity in order to respond to a large scale earthquake. Therefore, we have proposed an energy absorbing device with a double layer circular tube as a cell. In previous work, it has been shown that hysteresis occurs and absorbs the energy by friction that is generated between the outer layer and the inner layer. It is effective when inside shape of inner layer is defined as floral pattern. In this study, we considered to form the inner layer circular tube by forward and backward extrusion and to assemble with the outer layer circular tube at the same time. After forming, it is necessary to generate hysteresis around the entire circumference of the circular tube. Ideally, the inner layer circular tube is tightened to the outer layer circular tube. In this research, it was aimed to know the contact state between the outer layer and the inner layer after forming. Therefore, the influence of the presence or absence of the outer layer circular tube on formability was investigated. As a result, there was a tendency for large elastic strain to remain at the contact portion between the circular tubes when the outer layer circular tube was set. This means that the outer layer circular tube hinders elastic recovery of the inner layer circular tube. Therefore, it was confirmed that the inner layer circular tube was tightened by the outer layer circular tube. The same result was obtained when the inner shape of the inner layer circular tube was a flower pattern
The oldest portrait of a Japanese
In March, 1972, an old tomb was excavated in the Asukamura Village, Nara Prefecture» and, for the first time, painted portraits of sixteen Japanese, eight males and eight females, were found on mortared walls. The male figures were of about 35 cm in height and those of females about 38 cm
Magnetic phase diagram of three-dimensional diluted Ising antiferromagnet NiMg(OH)
- diagram of 3D diluted Ising antiferromagnet
NiMg(OH) with = 0.8 has been determined from
measurements of SQUID DC magnetization and AC magnetic susceptibility. At =
0, this compound undergoes two magnetic phase transitions: an antiferromagnetic
(AF) transition at the N\'{e}el temperature (= 20.7 K) and a reentrant
spin glass (RSG) transition at ( 6 K). The - diagram
consists of the RSG, spin glass (SG), and AF phases. These phases meet a
multicritical point ( = 42 kOe, = 5.6 K). The
irreversibility of susceptibility defined by (= ) shows a negative local minimum for 10 35 kOe,
suggesting the existence of possible glassy phase in the AF phase. A broad peak
in and at 20 kOe for (= 26.4 K) suggests the existence of the Griffiths
phase.Comment: 11 pages, 14 figures; J. Phys. Soc. Jpn. 73 (2004) No. 1 issue, in
pres
Edge state on hydrogen-terminated graphite edges investigated by scanning tunneling microscopy
The edge states that emerge at hydrogen-terminated zigzag edges embedded in
dominant armchair edges of graphite are carefully investigated by
ultrahigh-vacuum scanning tunneling microscopy (STM) measurements. The edge
states at the zigzag edges have different spatial distributions dependent on
the - or -site edge carbon atoms. In the case that the defects
consist of a short zigzag (or a short Klein) edge, the edge state is present
also near the defects. The amplitude of the edge state distributing around the
defects in an armchair edge often has a prominent hump in a direction
determined by detailed local atomic structure of the edge. The tight binding
calculation based on the atomic arrangements observed by STM reproduces the
observed spatial distributions of the local density of states.Comment: 9 pages, 11 figures, accepted for Physical Review
Berry's Phase for Standing Wave Near Graphene Edge
Standing waves near the zigzag and armchair edges, and their Berry's phases
are investigated. It is suggested that the Berry's phase for the standing wave
near the zigzag edge is trivial, while that near the armchair edge is
non-trivial. A non-trivial Berry's phase implies the presence of a singularity
in parameter space. We have confirmed that the Dirac singularity is absent
(present) in the parameter space for the standing wave near the zigzag
(armchair) edge. The absence of the Dirac singularity has a direct consequence
in the local density of states near the zigzag edge. The transport properties
of graphene nanoribbons observed by recent numerical simulations and
experiments are discussed from the point of view of the Berry's phases for the
standing waves.Comment: 6 pages, 4 figure
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