Section B
Joint Research

ISSP Activity Report 2002

Highlights of Joint Research
Synchrotron Radiation Laboratory
Synchrotron Radiation Laboratory (SRL) has been promoting the project for constructing a new synchrotron radiation facility dedicated to the science in VUV (or EUV) andSoft X-ray (SX) region, which has been discussed at thePanel on New Synchrotron Radiation Facility Project. The
new light source consists of a 1.8 GeV electron storage ringand the injector system. The normal cell lattice of the storage ring is a DBA type with twelve 6.2-m normal lengthstraight sections, two of which will be used for the injection
part and the RF cavity installation, and two 17-m longstraight sections. The injector consists of a 200 MeV lineac
and a 2.0 GeV booster synchrotron. The conspicuous featureof the new light source is that every part of the accelerators
is designed adapting to the “top-up injection” to overcome
the short lifetime of the electron beam in a storage ring operated with relatively low energy.
The details of the new facility have been discussed andplanned with nationwide supports by accelerator scientists
and engineers as well as researchers using synchrotron radiation. The results of the discussion are summarized as a
“New Synchrotron Radiation Project -Design Report- ” (inJapanese) in September 2002. The University of Tokyo
strongly endorsed the project to construct the proposed new
facility in the Kashiwa campus. The plan is supported not
only by researchers in academic institutions but also bioand chemical-industries. The figure below shows an imageof the new facility as constructed in the Kashiwa campus.
The staff members of SRL have been continuing the
research and developments of the light source, beamlines
and monochromators. The accelerator grougp of SRL is carrying out research works of the accelerator physics anddeveloping the accelerator-related technology, many ofwhich will be directly applied to the new light source. The
research highlight of 2002 is electron-beam size measurement with a newly developed beam profile monitor. The
monitor is a real-time and non-destructive monitor with ahigh spatial resolution and has a microscopic structure,
where two Fresnel zone plates constitute an X-ray imaging
optics. With this monitor, our group has succeeded in
obtaining a clear electron-beam image and measuring theelectron-beam size less than 10 µm in the KEK-ATF damping ring.
On the other hand, the branch laboratory at KEK-Photon

Factory maintains an undulator called Revolver, two beamlines and three experimental stations for angle-resolved photoelectron spectroscopy (ARPES), spin- and angle-resolved
photoelectron spectroscopy (SARPES) and soft X-ray emission spectroscopy (XES), which are fully opened to outsideusers. The SRL staffs not only serve the outside users withtechnical support and advices, but also carry out their own
research works on advanced solid state spectroscopy as wellas instrumentation. In the fiscal year of 2002, the operation
time of the beamlines was more than 5000 hours and thenumber of the users was more than 200.
The scientific highlights of the beamlines achieved in
2002 are found in the studies of the electronic structures of aferroelectric Bi4Ti3O12 observed by XES, of an alkalinemetal doped C60 adsorbed on Si surfaces studied by ARPES.
The SARPES experiments on Co/Pd(111) shows that the reorientation of the magnetization direction observed in Co
films is the result of the increase of Co 3d electrons withorbital moment parallel to the surface as the Co film thickness increases.

Neutron Scattering Laboratony
Since 1961, the ISSP has been playing a central role inneutron scattering activities in Japan not only by performing
its own research programs but also by providing a generaluser program for the university-owned various neutron scattering spectrometers installed at research reactors of JAERI(Tokai). By spending 5 years staring from 1988, the ISSP
constructed total 8.5 highly-sophisticated spectrometers bothin a reactor hall and in a guide hall of the refurbished JRR3M reactor (20 MW) with cold source. In addition, Tohoku
University owns 3.5 spectrometers and Kyoto University 1;
therefore, total 13 spectrometers belong to the university
while JAERI owns 9. In order to fully utilize these facilities,
the previous Neutron Scattering Division of ISSP at Tokyo
was promoted to the present Neutron Scattering Laboratory
at Tokai in 1993. Since then, close to 300 proposals are submitted for the ISSP general user program for neutron scattering research each year, and the number of visiting users
under this program reaches over 7000 (person-day/year).
Major research areas are solid state physics (strongly correlated electron systems, high Tc superconductors, heavy
fermion systems, low dimensional magnetism, high-pressure
physics etc.), fundamental physics and neutron beam optics,
polymer, chemistry, biology, and materials sciences.
Triple axis spectrometers and a high resolution powder
diffractometer were utilized for a conventional solid statephysics and a variety of research fields on hard-condensed
matter, while in the field of soft-condensed matter physics,
researches were mostly carried out by using the small angle
neutron scattering (SANS-U) and/or neutron spin echo(NSE) insturuments. In the fiscal year of 2002, the research
topics on the hard-condensed matter science covered stripe
order in high-Tc superconductors, and closely related 2
dimensional systems, charge and orbital ordering in CMR
manganites, quadrapolar ordering in rare-earth based intermetallic compounds, spin dynamics of low dimensional
dimmer systems, etc. On the other hand, the research topics
on the soft-condensed matter science covered structure char-

ISSP Activity Report 200229

acterization of polymer blends, micelles, amphiphilic polymers block copolymers, liquid crystals, proteins, inorganic
gels, dynamics of brush-polymers on surface, slow dynamics of surfactants, pressure dependence of dynamics ofamphiphilic membranes, and so on. The details of individual
studies are reported in the NSL-ISSP Activity Report 2003
(vol.10).

Supercomputer Center
The supercomputer system in the Supercomputer Centerof the Institute (SCC-ISSP) is placed at the service of general researchers of condensed matter physics through the User
Program conducted by the Materials Design andCharacterization Laboratory (MDCL). One of its aims is toselectively promote and support huge computations which
are hardly carried out on other computers such as work-station clusters in individual laboratories.
The SCC-ISSP main system consists of two supercomputers. Hitachi SR8000/60, called System-A, is a distributed-memory-type parallel supercomputer with 60 nodes,
640 GB memory in total and 12×60 GFlops peak performance. On the other hand, SGI Origin 2800/384, called
System-B, is a massively parallel supercomputer with
192 GB memory in total and 0.8×384 GFlops peak performance.
A project(s) can be proposed by any staff in universities
or public research institutes in Japan. The projects proposed
are judged by the Steering Committee of the SCC-ISSP,
under which the Supercomputer Project Advisory
Committee is formed to review proposals. More than half ofthe members of each committee are those in other institutions than the ISSP. The number of projects, the total points
applied and approved in this year are listed on Table. 1
The research projects carried out on the system covervarious fields in the condensed matter physics. They areroughly classified into the following three (the number ofprojects approved):·First-Principles Calculation of Materials Properties (52)·Strongly Correlated Quantum Systems (60)
·Cooperative Phenomena in Complex, Macroscopic

Systems (22)
All the three involve both methodology of computationand its applications. The results of all the projects are reported in ‘Activity Report 2002’ of the SCC-ISSP. In the report
the following five invited articles are included in this year:“Equilibrium and off-equilibrium simulations of the threedimensional Heisenberg spin glass (S-class project)” by
Hikaru Kawamura and Koji Hukushima,“First-principles study with Diffusion Monte Carlo code”
by Ryo Maezono,“Theoretical Analyses of Electric-Current Related
Phenomena at Surface Nanostructures under Strong
Local Electric Field” by Satoshi Watanabe, Yoshihiro
Gohda, Shinnosuke Furuya, Noriko Tanaka, Chunping
Hu and Hideomi Totsuka,“Monte Carlo study of ferromagnetic transition in doubleexchange” by Yukitoshi Motome and Nobuo Furukawa,“Large Spins and High-Order Interactions” by Naoki
Kawashima and Kenji Harada.
Based on the discussions at the ISSP Workshop“Computational Physics for Condensed Matter Research”
held in November 2002, the home page
http://www.issp.u-tokyo.ac.jp/public/cmp
and the mailing list ‘cmp-ml’ were set up for communicating information not only on the SCC-ISSP but on general
research activities in the field of ‘Computational Material
Physics’.

For System-A 1 K point corresponds to charge for CPU time of about 0.43 hours by one processing element, while the corresponding figure is 2.32 hours for System-B. For one of the D class projects, a special queue which exclusively uses 2 nodes ofsystem-A was allowed to perform extremely long-time jobs necessary.

30

ISSP Activity Report 2002

High Resolution Atomic Force Microscopy
by Detection of a Single Chemical
Bonding
T. Eguchi, Y. Hasegawa and T. Sakurai
Atomic force microscopy (AFM) provides surface
images of various materials regardless to its electrical conductance by detecting a force acting between the sample surface and probe tip. Recent developments for a force detection technique make us possible to take images withnanometer-scale spatial resolution. Compared with scanningtunneling microscopy (STM), however, its spatial resolution
has been still limited. One of the reasons for the limited resolution is a significantly large site-insensitive backgroundcomponent due to the van der Waals (vdW) force. In thisstudy we succeeded in achieving highly resolved AFM
imaging by reducing the background force and detecting aforce arising from a single chemical covalent bonding byusing small oscillation amplitude of the cantilever and an
atomically sharp tip [1]. Since the chemical bonding is innature a short range force, it works as a extremely sensitive
probe, similar with the tunneling current of STM.
Figure 1 shows a typical AFM image taken in this study.
In the image, individual adatoms of the dimer-adatom-stacking fault (DAS) structure are clearly imaged. In addition,
hump features are obviously observed at the sites exactly
corresponding to the rest-atoms. In the area where adatom is
missing, the second-layer atoms are also clearly resolved.
In order to analyze what kinds of forces are working
between the sample and probe tip, we measured the force asa function of the tip-sample distance (i.e. force curve). Sucha force profile is shown in Fig. 2. When the tip and sample
are separated more than 1nm, the force varies gradually, andat the proximate distances below 1 nm, the force changes
steeply. The gradually-varied force is due to the long-range
vdW force, and the steep one is due to a chemical covalentFig. 2. A frequency shift versus tip-sample distance curve (force curve) measured on the Si(111)-(7×7) surface. Experimental data points are marked witha red filled circle. The fitted line is drawn with a red line. A blue line depicts
a component by the long-range vdW force, and a green circle shows theexperimental data points minus the component of the long-range force. The
green line is a component due to the short-range chemical force. The sum of
the blue line and green line should be equal to the red fitted line. Inset: Modeltip shape deduced from the fitting depicted with a side view of the surface
structural model. Model A is fitted nicely with our experimental data andmodel B, a parabolic shape with an apex radius of 4 nm, is the one used forfitting in other works. A simulated long-range force curve with tip B is drawn
in the plot (orange line), demonstrating a strong reduction of the backgroundusing tip A.

bonding between the atoms of the sample surface and Si tip
apex. From a fitting with known parameters for the Si-Si
bonding, it is found that the chemical bonding is due to asingle bonding.
Since the total vdW force is a sum of vdW working on
individual atoms composing the sample and tip, the shape ofthe tip can be deduced from the force profile, and found tobe like tip A shown in an inset of Fig. 2. It should be notedthat the tip apex is very sharp. As a comparison a force profile for a blunt tip (tip B) is calculated and plotted with anorange curve in Fig. 2. Obviously, with tip B the vdW force
is large, dominating over the chemical force. It is thus difficult to obtain highly resolved images with tip B.
This study implies that characterization of the AFM tip
in nanometer scale, not only on the apex atoms but also its
shape near the apex, is important and critical for AFM highresolution imaging.
Reference[1] T. Eguchi and Y. Hasegawa, Phys. Rev. Lett., 89, 266105 (2002).
Authors

T. Eguchi, Y. Hasegawa, and T. Sakuraia
aInstitute for Materials Research, Tohoku University

LEED and STM Study of GaP(111)B
Reconstructed Surface
K. Hattori and F. Komori

Fig. 1. (a) An atomically resolved AFM image of the Si(111)7×7 surface. The
observed area of the AFM image is 7.5 nm × 3.0 nm. (b) Top view of the
DAS structural model of the Si(111)7×7 surface. (c) A cross-sectional plotmeasured on the long diagonal line of the 7×7 unit cell drawn in (b), together
with a side view of the DAS structural model, demonstrating a precise fittingof adatom and rest-atom positions.

Gallium phosphide is one of the fundamental III-V compound semiconductors for optoelectronic devices. Various
works on GaP crystals coupled with other materials havebeen performed to educe valuable functions of these systems. We have studied GaP(111)B (i.e., (-1-1-1), phosphorus face) reconstructed clean surface with low-energy electron diffraction (LEED) and scanning tunneling microscopy(STM). This surface is important because it has been used
for the transparent substrate of GaAlAs diodes and for the

ISSP Activity Report 2002

31

The reciprocal lattice of the surface model with the random mixture of the two reconstructed units, ((3 -1), (2 5))
and ((4 1), (2 5)), well explains the obtained LEED patterns(e.g., Fig.1) assuming the same elements positioned at theSTM protrusions. Further analysis such as LEED I-V measurement will solve the atomic structure of the reconstructed
GaP(111)B surface, based on these results.
References[1] A.J. Van Bommel and J.E. Crombeen, Surf. Sci. 93, 383 (1980).
[2] X. Wang, X.Y. Hou, X.M. Ding, G.S. Dong, X.K. Lu, and P.
Chen, in "Surface Physics and Related Topics: Festschrift for Xide
Xie", edited by F.-J. Yang et al., (World Scientific Publishing,
Singapore, 1991), p. 326.
Fig. 1. A typical LEED pattern of GaP(111)B reconstructed surface at 30 eV.
The pattern includes many super-spots (e.g., F, S, S' and S") arising from thesurface reconstruction.

buffer layer of well-growth InN film with an excellent electronic transport property, for instance.
The reconstructed LEED pattern of GaP(111)B surface
is very complex. Figure 1 shows a typical pattern at 30 eV.
So far, there have been two different explanations for thereconstructed unit with the assumption of a single domain
formation on this surface; Bommel and Crombeen reported
17×17 reconstruction [1], while Wang et al. suggested√247×√247-R22.7º [2]. However, we found using STM thatthe reconstructed surface consists of six domains with stripe
pattern. Figure 2(a) shows an STM image of the multiple
domain area. The stripe directions are tilted from three〈-1-12〉 (i.e. [-1-12], [-12-1] and [2-1-1]) directions at 6.8º,
and the stripe period is 1.30 nm. Therefore, the surface consists of six equivalent mirror-symmetric domains (threepairs of twin domains, A and B, C and D, and E and F).
A magnified STM image of the stripe structure is shownin Fig. 2(b). The reconstructed surface unit can be recognized by analyzing the arrangement of the atomic protrusions. On this surface, surprisingly, we found that two different unit cells exist; the same unit is repeated along thestripe but either the same or the different unit (with almost
the same possibility) is arranged for the inter stripe direction.

Fig. 2. STM images of GaP(111)B reconstructed surface, (a) 150 nm×90 nm
area showing multiple domains with stripe patterns (some with lines for theeye guide), and (b) 5.4 nm×6.3 nm area the magnification of the stripe pattern
In Fig. (b) the black circles present the origins of surface reconstruction units,
and each unit includes several protrusions. We can recognize the co-existenceof the two different units.

32

ISSP Activity Report 2002

Authors
K. Hattoria, K. Ishiharaa, Y. Miyatakea and F. Komori
aGraduate School of Materials Science, Nara Institute of Science andTechnology

Charge Transfer at Oxide Interfaces
H. Kumigashira and M. Lippmaa
Oxide surfaces and interfaces often behave quite differently from bulk crystals. This can be seen easily in thin layers of La0.6Sr0.4MnO3 grown on various oxide surfaces.
Although the bulk material is a ferromagnetic metal below
about 300 K, single unit cell layers are usually insulating.
Such a dramatic change in transport properties is caused bya charge transfer between the film and the underlaying layer,
effectively altering the carrier concentration in the thin film.
Such changes have a large impact on the properties of oxide
superlattices and heterostructures.
Our aim is to understand how the electronic structure of
the interface layer deviates from the bulk by measuringhigh-resolution photoelectron emission spectra of the Mn
valence band close to an interface [1]. We use a compact
pulsed laser deposition chamber attached to a photoelectron
spectrometer at BL2C of the Photon Factory to grow a thick
La1-xSrxMnO3 (LSMO) film, covered by a thin layer of
La1-xSrxFeO3 (LSFO). The cover layer thickness is usually 1
to 3 unit cells. The probing depth of the photoelectron emission measurement is less than 10 unit cells. The contributions to the valence band spectrum by the bulk LSMO film
and the thin LSFO cover layer can be separated by using aresonant emission technique, as shown in Fig. 1.
The intensity of the photoemission peak at 1 eV below
the Fermi level is a direct measure of Mn 3d electron density

Fig. 1. Photoemission spectrum of a single unit cell film of La0.6Sr0.4FeO3 on
a La0.6Sr0.4MnO3 surface. Resonant emission spectra of the valence bandshow the contribution of the Fe oxide layer and the top part of the bulk Mnoxide to the total emission intensity.

Fig. 2. Resonant Mn photoemission spectra of thick (A) La0.45Sr0.55MnO3 and(B) La0.6Sr0.4MnO3 films. A drop in the eg state population in the topmost
layer of the La0.6Sr0.4MnO3 film as a result of charge transfer toLa0.6Sr0.4FeO3 can be seen in (C) and (D). The La0.6Sr0.4FeO3 cover layer
thickness was 1 unit cell in (C) and 2 unit cells in (D).

in the eg levels. For calibration purposes we have measured
the intensity of this peak for a series of thin film samples
with a different hole concentration x. A systematic drop inelectron density is observed as the hole concentration x isincreased, as shown by spectra (A) and (B) in Fig. 2.
A part of the LSMO (x=0.4) film was covered with one
or two monolayers of LSFO (x=0.4) for charge transfer
measurements at the LSMO/LSFO interface. A sketch of thesample geometry is shown in the inset in Fig. 2. As shownby spectrum (C) in Fig. 2, the presence of a single monolayer of LSFO on top of LSMO (x=0.4), reduces the electron
density to a level which corresponds to a bulk LSMO
(x=0.55) film. An even greater drop is observed when the
thickness of the LSFO layer is doubled. This is a clear indication that there is indeed a large transfer of electrons from
the Mn ions to Fe. The change in the effective carrier concentration is very large and can easily transform the topmost
few unit cells of the LSMO film into an insulating or an
antiferromagnetic phase.
Reference[1] H. Kumigashira, K. Horiba, H. Ohguchi, K. Ono, M. Oshima, N.
Nakagawa, M. Lippmaa, M. Kawasaki, H. Koinuma, Appl. Phys.
Lett., 82, 3430 (2003).
Authors
H. Kumigashiraa, K. Horibaa, M. Lippmaa, T. Ohnishi
aDeptartment of Applied Chemistry, University of Tokyo.

intensity is extremely weak. On the other hand,Bremsstrahlung Isochromat Spectroscopy (BIS) in VUV and
X-ray region is rather easy to observe, thus these spectra
have been observed for many substances including single
crystal Ni.
Figure 1 shows energy diagram of IPES. In normal
process of IPES, incident electron undergoes transition to
conduction band with emitting X-ray.
|dn〉+e- → |dn+1〉 + hν
(1)
When the excitation energy is lower than absorption edge ofcore electron, only the normal process takes place. On theother hand, core electron is excited to conduction band orcontinuous energy level, when the energy of excitation electron is higher than absorption edge. In case that the excitedelectron is ejected to continuous level, higher-level electron(e.g. valence band) undergoes transition to core hole withemitting X-ray fluorescence. The fluorescence has typicalenergy for the substrate and does not vary with excitationenergy. In other case that typically the excitation energy is
the same as core absorption energy, intermediate excitation
state |cdn+2〉 is created without radiation. Then, the state
decays with emitting X-ray.
(2)|dn〉+e- → |cdn+2〉 → |dn+1〉 + hν,
where c denotes a core hole. Since the process (1) and (2)have same initial and final state, these two processes resonate with each other. In the case of Ni, however, nominal
3d 9 state cannot have 3d n+2 state. Thus, the 3d 9 state would
not be enhanced in the resonance. It is suggested from many
experiments that Ni has other state; 3d10 and 3d 8 [1, 2]. The
3d 8 state would be enhanced in the resonance.
We observed the Resonant IPES of single crystal Ni in
SX region for the first time. Clean surface of Ni (110) was
obtained by Ar-ion bombardment and annealing at temperature of about 700°C. Cleanness of the sample was checkedby Auger spectra and LEED measurement.
Figure 2 shows resonant IPES spectra of Ni (110). On(66.0 eV) and off (71.9 eV) resonant spectra are shown. Ni
3d-3p fluorescence peak that have energy of about 65.5 eV
is observed in both spectra. The main peak just above EF is
Ni 3d structure, while Ni 4sp is observed at 10~15 eV.
Though the 3d and 4sp band show band dispersion, it cannot
be discussed here, because the excitation electron is not normal incidence and the wave vector of electron is larger thanzone boundary. The 3d band structure becomes weak in theresonant spectra. This fact means the 3d structure originatedfrom 3d 9 components. Satellite structures are also observed

Resonant Inverse Photoemission Studyof Ni (110)
Y. Tezuka and S. ShinResonant inverse photoemission spectra (RIPES) of single crystal Ni was observed near Ni 3p absorption edge. Ni
is typical itinerant ferromagnet and it has nominal 3d 9 electronic structure. That is, the Ni has only one 3d hole in conduction band. When it is magnetized, majority spin band isfilled with electron, while minority spin band has one 3d
hole.
Inverse photoemission spectroscopy (IPES) observes thetotal density of state (DOS) of unoccupied state. Soft X-ray(SX) IPES have never been observed until recently, since its

Fig. 1. Energy diagram of IPES. Core electron is excited to conduction bandor continuous energy level, when the energy of excitation electron is higher
than binding energy of core electron.

ISSP Activity Report 2002

33

Fig. 2. RIPES spectra of Ni (110). On (66.0 eV) and off (71.9 eV) resonant
spectra are shown. Dots are observed data and red lines are smoothed data. Ni
3d-3p fluorescence peak is observed in both spectra. Main peak just above EF
is Ni 3d band, while Ni 4sp band observed at 10~15 eV. Satellite structures
are observed at about 2 and 4 eV in resonant spectra.

at about 2 and 4 eV in resonant spectra. We have observed
the IPES of polycrystalline Ni that was prepared by evaporation method. In those spectra, Ni 3d band was observed
rather wide and Ni 4sp band could not be observed.
Tanaka and Jo calculated RIPES spectra of Ni on thebasis of the Anderson impurity model. In their calculation,
Ni has 10~20 % 3d 8 ground state. They suggested that two
satellite structures should be observed at about 2 and 4 eV
and these are enhanced at the Ni 3p core threshold [3]. In
our spectra, satellite structures are observed at about 2 and
4 eV, though the intensities are very weak. We think thesesatellite structures originate from the 3d 8 component. The
RIPES spectra in this study give us a direct evidence of 3d 8component in Ni metal.
References[1] T. Jo and G. A. Sawatzky, Phys. Rev. B 43, 8771 (1991).
[2] G. van der Laan and B. T. Thole, J. Phys. Condens. Matter 4,4181 (1992).
[3] J. Phys. Soc. Jpn, 66, 1591 (1997).
Authors
Y. Tezukaa, D. Nakajimaa, Y. Miyazakia, K. Kanaib, H. Ishiic, S.
Nozawad, R. Eguchi, S. ShinaDepartment of Science and Technology, Hirosaki University
bDepartment of Science, Nagoya University
cTaiwan APCSCT
dPhoton Factory, KEK

Ultrahigh-Resolution Photoemission
Spectroscopy of The Binary Cd5.7Yb
and Its Crystalline Approximant Cd6Yb
R.Tamura and S. Shin
The recently discovered stable binary Cd5.7Yb quasicrystal (i-phase) [1] is of particular interest from the view of PE
spectroscopy: First, there exists a cubic crystalline approximant(1/1-Cd6Yb) in the vicinity of the i-phase composition,
thus enabling us to investigate the influence of quasiperiodicity on the electronic structure. Second, since it contains arare-earth element whose 4f states lie close to EF [2] andsuch well localized 4f states are likely to produce sharp

34

ISSP Activity Report 2002

Fig. 1. (a)Low-temperature He-I PE spectra of i-Cd5.7Yb and 1/1-Cd6Yb withan energy resolution of 20 meV. The inset shows deconvolution of the iCd5.7Yb spectrum. (b)The same spectra superimposed on one another for abetter comparison.

final-state multiplet structures in the PE spectrum, we expectthat surface sensitive PE technique allows us to investigatechanges of the electronic structure in the surface region of
the solid with high resolution [3].
Figure 1 (a) presents low-temperature PE spectra for iCd5.7Yb and 1/1-Cd6Yb measured at 5.7 K and in Fig.1(b)are shown the same spectra superimposed on one another inorder to clarify the difference between the two compounds.
First of all, a common feature is observed in both spectra of
i-Cd5.7Yb and 1/1-Cd6Yb: Two distinct peaks appear around
BE=-0.7 and -2.0 eV. Comparing with the theoretical DOS
of 1/1-Cd6Yb [2], the observed peaks can be readily
assigned to the Yb 4f states. This is further confirmed by thefact that the estimated energy separation of 1.27 eV between
the peaks corresponds exactly to the atomic spin-orbit energy 1.27 eV and hence we conclude that the peaks are due tothe 4f 7/2 and 4f 5/2-derived states as appropriate. In Fig.1(b),we notice that the peak positions of the Yb 4f doublet are
deeper for the i-phase than for the approximant, by about
25±5 meV. This implies that the electronic system aroundYb atoms is more stable in the i-phase than in the approximant.
A striking feature in Fig.1 is the existence of two humps
at higher binding energies side of the corresponding 4f
peaks, as clearly seen at around BE=-1.4 eV and -2.7 eV for
the approximant while they are mixed with the doublet ofthe 4f states for the quasicrystal. The locations of the humps
were determined to be -1.40±0.01 and -2.68±0.01 eV for
1/1-Cd6Yb and -1.08±0.05 and -2.37±0.05 eV for i-Cd5.7Yb.
In rare-earth-metal compounds, such extra humps in thevicinity of well localized states such as the 4f states are wellknown for the surface core-level shifts (SCS), which reflectchanges of the electronic structure in the surface region. Theenergy separation of the humps is about 1.3 eV for bothcompounds and agrees well with the 4f splitting energy ofthe bulk states, confirming that they are due to the 4fderived states. The lowering of the binding energy at thesurface indicates that the binding energies of surface atoms

are higher than those of bulk atoms. The surface components are shifted to higher binding energies by 0.68±0.01 eV
for 1/1-Cd6Yb and by 0.36±0.05 eV for i-Cd5.7Yb. The existence of the SCS themselves unambiguously verifies that theelectronic structure at the surface is different from that in thebulk in the case of the quasicrystal and the approximant. The
present experiment is the first direct observation of the surface states in the quasicrystalline materials.
Next we focus on the structure in the vicinity of EF in the
PE spectra. As seen from Fig.1(a), a decrease of the spectral
intensity towards EF which is well distinguished from theFermi cut-off is observed for both phases and this trend
becomes enhanced near EF. Moreover, the intensity depression at EF is found to be considerably stronger for the iphase than for the approximant (Fig.1(b)), which clearlyshows that the dip at EF is deeper in the quasicrystal than in
the cubic approximant. The stronger intensity decrease nearEF, i.e. less occupied states in the vicinity of EF, in i-Cd5.7Yb
directly indicates a larger energy gain due to the dip formation in the i-phase than in the approximant.
References[1] A.P. Tsai et al., Nature 408, 537 (2000).
[2] Y. Ishii et al., Phys. Rev. Lett. 87, 206408 (2001).
[3] R.Tamura et al., Phys. Rev. B 65, 224207 (2002).
Authors
R. Tamuraa, Y. Muraoa, S. Takeuchia, T. Kiss, T. Yokoya, and S. ShinaDepartment of Materials Science and Technology, Tokyo Universityof Science

Discovery of Missing Link: IV. Spin-1/2
Spinel Oxide MgTi2O4
N. Nakayama and Y. Ueda
The spinel oxides AB2O4 have displayed a variety ofelectromagnetic properties such as superconductivity, heavy
fermion behavior, charge order, and unusual magnetic properties. One important structural property of the cubic spinel
structure is a three-dimensional (3D) network of cornersharing tetrahedra formed by B-cations (pyrochlore lattice).
This structural feature has drawn much attention as a geometrically frustrated 3D lattice. An antiferromagnetic

Fig.1. Temperature dependence of magnetic susceptibility and resistivity for
MgTi2O4. MgTi2O4 shows a transition from metal to spin-singlet insulator at
260 K. This transition is accompanied by a structural change from cubic totetragonal. The inset is a schematic illustration of the spinel structure composed of BO6 octahedra in AB2O4 and a three-dimensional network of corner-sharing tetrahedra formed by B-cations (pyrochlore lattice). The dottedline indicates a certain chain of edge-sharing BO6 octahedra.

Fig. 2. [110]-zone electron diffraction patterns below (a) and above (b) thetransition temperature (260 K) in MgTi2O4. The lattice image (c) of the lowtemperature phase shows clear lattice fringes of the fundamental spinel lattice. It also shows (001) lattice fringes as marked by an arrow. The perspective view (d) of the image (c) along the [1-10] direction reveals that the (001)lattice fringes appear almost whole the observed region but with several
defects.

exchange interaction among Heisenberg spins on the neighboring B-cations maximizes frustration in the magnetic
order. Such geometry of the crystal structure also produces
strong frustration in charge ordering.
It is well known that quantum effects on spin fluctuations are markedly enhanced in the S=1/2 (d1) system. Veryrecently, the exotic quantum ground state was theoretically
predicted on the pyrochlore lattice with S=1/2. Although thesearch for a spin-1/2 compound has been motivated by its
intriguing quantum phenomena, it has been missing in thespinel family.
We have succeeded in synthesizing MgTi2O4 that havebeen expected to realize the pyrochlore lattice with S=1/2,
and investigated the structural and electromagnetic properties. We found a metal-insulator transition at 260 K (Fig. 1)[1]. The ground state could be spin singlet, because the magnetic susceptibility obtained by subtracting the Curie tail at
low temperature is comparable to that for other spin-gap
systems and there is no evidence for magnetic order in µSR
experiments. The transition is accompanied by a structuraltransition from cubic to tetragonal. Shown in Fig. 2 are thechange of the electron diffraction pattern below and above
260 K and the high-resolution TEM lattice image of the lowtemperature phase. The electron diffraction pattern at 115 K
shows very weak superlattice spots in addition to the fundamental spots (Fig. 2(b)) of spinel lattice, indicating the symmetry breaking. They appear only at the forbidden reciprocal lattice points of the cubic spinel and no spot indicating
the multiplicity of the supercell was observed.
These results indicate a Peierls-like transition in
MgTi2O4. Why does the Peierls-like transition inherent in
1D system occur in the 3D spinel system? As a possible scenario, an orbital ordering might play an important role in thePeierls-like transition of MgTi2O4. In the cubic spinel structure, the TiO6 octahedra are arranged in chains through edge
sharing, as shown in the inset of Fig. 1. If there exists orbital

ISSP Activity Report 200235

ordering along each chain direction, the dimensionality islowered from 3D to 1D, which is responsible for the Peierls
transition.
Reference[1] M. Isobe and Y. Ueda, J. Phys. Soc. Jpn. 71, 1848 (2002).
Authors
N. Nakayamaa, M. Isobe, M. Ichihara, and Y. Ueda
aFaculty of Engineering , Yamaguchi University

Room Temperature Synthesis of
Carbon Nanotubes by Electrochemical
Deposition using Organic Solution
H. Yokomichi, M. Ichihara and F. Sakai
Carbon nanotubes have been commonly synthesizedusing a wide variety of chemical vapor deposition (CVD)methods [1,2]. As the vapor phase synthesis, arc discharge
and laser ablation techniques have also been used for nanotube synthesis. In addition, an arc discharge [3] and thermal CVD [4] under high magnetic field of 10 T have been
employed for nanotube synthesis. However, synthesis temperature of nanotubes by the methods, at least 550 °C, ishigher than that of graphite-like carbon films. In the present
study, we show room temperature synthesis of carbon nanotubes and carbon nanowires, for the first time, by an electrochemical deposition technique under a liquid phase oforganic solution using a metal catalyst. Nanocarbons withsea urchin-like and onion-like structures have also been successfully synthesized using the electrochemical technique.
Electrochemical deposition has been carried out by
applying a DC voltage in organic solutions such as CH3OH
and C2H5OH. The p-type crystalline silicon (c-Si) was used
for the substrate. A graphite rod and the c-Si substrate wereused for a cathode and an anode, respectively. The metal
catalyst was dissolved into the solution.
The c-Si substrates colored dark black after the electrochemical deposition with and without the metal catalyst.
SEM images of the deposits without Ni catalyst indicate that
amorphous carbon films with a roughened surface andFig. 2. TEM image of the deposits synthesized using C2H5OH with a Ni catalyst. The metal catalyst was dissolved into the solution.

graphite grains of a few micron sizes were deposited on thesubstrate. The carbon nanotubes and nanowires were notdiscernable for all the case. On the contrary, nanocarbons
with various structures, e.g., sea urchin-like structures (a)and nanowires (b), were observed for the deposits using
C2H5OH with Ni(NO3)n •mH2O as shown in Figs. 1 (a) and(b), depending areas of the samples. The existence of carbon
nanotubes is shown by the TEM image in Fig. 2 for thedeposits using C2H5OH with the metal catalyst, althoughcarbon nanotubes were not discernable for the deposits without the catalyst.
Although the growth mechanism is not clear, we speculate that the metal anions are attached on the c-Si substrate
at an initial stage and then the metal grains act as a nucleation and growth centers of nanocarbons. In fact, the metal
films were grown for a shorter time, when the solution withmuch more metal anions was used. Therefore, nanocarbons
are grown from carbon anions generated by the applied highelectric field by the aid of metal grains created in the initialstage. The Ni metals were detected by EDS measurements
for the regions corresponding to the SEM images shown in
Figs. 1 (a) and (b). However, the Ni grains were not explicitly discernable by electron reflection images for the regions
corresponding to the SEM images. These results suggest thatthe metal grain sizes are small, e.g., below a few tens of nm.
The growth for various types of nanocarbons may be attributed to shapes of the metal grains determined by the strengthof applied electric fields and the surface morphology of thesubstrate, because the types of nanocarbons have beenreported to depend on the size of metal grains in the case ofthermal CVD [5].
We would like to thank Dr. N. Kishimoto of National
Institute for Materials Science for useful suggestions.
References[1] W. Li et al., Science 274, 1701 (1996).
[2] M. Terrones et al., Nature 388, 52 (1997).
[3] H. Yokomichi, H. Sakima, M. Ichihara, F. Sakai, K. Itoh and N.
Kishimoto, Appl. Phys. Lett. 74, 1827 (1999).
[4] H. Yokomichi, F. Sakai, M. Ichihara and N. Kishimoto,Transactions of the Materials Research Society of Japan, in press.
[5] H. Yokomichi, F. Sakai, M. Ichihara and N. Kishimoto. J. NonCryst. Solids 299-302, 868 (2002).

Fig. 1. SEM images of various nanocarbons: sea urchin-like structures (a) andnanowires (b) synthesized using C2H5OH with a Ni catalyst. The metal catalyst was dissolved into the solution.

36

ISSP Activity Report 2002

Authors
H. Yokomichia, M. Ichihara and F. Sakai
of Electronics and Informatics, Toyama Prefectural
University.

aDepartment

X-ray and Optical Studies on
One-Dimensional Organic Conductors
T. Kawamoto, T. Mori, J. Yamaura,and H. Tajima
Several TTP series donors [tetrathiapentalene (TTP)
series donors] with methylthio groups realize one-dimensional electronic states owing to the side-by-side steric hindrance of the methylthio groups [1]. (ChTM-TTP)2X(X=GaCl4, AuBr2, and Au(CN)2) are quasi-one-dimensionalorganic conductors with dimerized donor stacking structures[2,3]. The crossover from a metal to a charge localized statetakes place around 150 K (for the GaCl4 salt), followed byan antiferromagnetic transition at 32 K [3]. (ChTM-TTP)2X
is the first TTP conductor whose ground state is an antiferromagnetic insulator. Although these physical properties
resemble (TMTTF)2Br, the charge localization temperatureand the Néel temperature are much higher than those of the
TMTCF salts.
Low-temperature crystal structure and optical propertiesof the quasi-one-dimensional organic conductor (ChTMTTP)2GaCl4 have been investigated at the X-ray laboratory
and the Spectroscopy laboratory in the Materials Design andCharacterization Laboratory. As the temperature lowers, thedisordered anion structure transforms to an ordered statewith a superstructure wave vector of q=(1/2, 0, 1/2) (Fig.1).
The peak intensities of the superlattice gradually increase in
the metallic region, and are saturated below 150 K; this indicates that the charge localization below 150 K is independent of the superlattice. The reflectance spectra of (ChTMTTP)2X suggest the existence of moderate interchain interactions (Fig.2). The transverse interactions are more pronounced in the GaCl4 salt (t⊥/t|| ≈ 1/7) than the AuBr2 andAu(CN)2 salts. The low-temperature optical reflectance of
the GaCl4 salt shows no significant change, indicating that
(ChTM-TTP)2GaCl4 goes to an insulating state with a smallenergy gap, in consistent with the transport property. The
low-frequency peak in the chain-axis optical conductivity is
attributed to electron correlation,

Fig. 2. (a)Reflectance spectra and optical conductivities of (ChTMTTP)2GaCl4 at room temperature. The solid lines in upper figure are theDrude-Lorentz fits. (b)Energy band structure and the Fermi surface of(ChTM-TTP)2GaCl4 calculated from the transfer integrals obtained throughthe optical experiment at room temperature.

though the expected on-site Coulomb repulsion U is relatively small. This scenario is consistent with the antiferromagnetic ground state of (ChTM-TTP)2X.
References[1] T. Mori et al., Mol. Cryst. Liq. Cryst. 284, 271 (1996).
[2] M. Ashizawa et al., Chem. Lett. 649 (1997).
[3] T. Kawamoto et al., Bull. Chem. Soc. Jpn. 75, 435 (2002).
Authors
T. Kawamotoa, M. Ashizawaa, T. Moria, T. Yamamoto, J. Yamaura,and H. Tajima
aDepartment of Organic and Polymeric Materials, Tokyo Institute ofTechnology

The Magnetization Plateau andCommensurate - Incommensurate
Transition in the 2D Triangular
Antiferromagnet Cs2CuBr4
Y. Fujii and M. Takigawa

Fig. 1. X-ray oscillation photograph of (ChTM-TTP)2GaCl4 at room temperature (a) and 16 K (b) showing the q =(1/2,0,1/2) scattering (white arrows).
The original axes are shown by black arrows.

The quasi-two dimensional antiferromagnet Cs2CuBr4,
where the magnetic Cu2+ ions with S=1/2 form a distorted
triangular lattice in the bc-plane, has attracted keen attention, since a plateau was observed in the magnetization
curve at one-third of the saturation magnetization when themagnetic field was applied along the b- or c-axes [1]. Recent
neutron diffraction experiments suggested a cycloidal
incommensurate spin ordering propagating along the b-axis
with TN=1.4 K at zero field. In order to obtain microscopic
insight into the spin structure and the spin dynamics in
Cs2CuBr4, we have performed 133Cs NMR experiments inthe temperature range down to 0.4 K under the magnetic
field up to 15.9 T. A single crystal of Cs2CuBr4(2 mm×3 mm×4 mm) was used.
Figures 1 [A] and [B] show the NMR spectra obtained
for the magnetic fields applied along the b- and a-axie,

ISSP Activity Report 2002

37

Fig. 1. The NMR spectra of 133Cs nuclei in Cs2CuBr4 for the magnetic fieldalong the [A] b- and [B] a-axie. Only the spectrum [A](b) obtained in theplateau phase shows discrete reaonance lines, while others exhibit continuous
spectra. The proposed spin structure is shown for each spectrum.

respectively. Note that the spectrum [A]-(b) was measured
in the 1/3-plateau phase, which occurs for the field range
14.0-15.5 T for H//b [1], while the others were obtained outside the plateau. In all cases, we observed two distinct 133Cs
resonance lines, which correspond to tow inequivalent sites,
A and B, in the unit cell, although we have been yet unable
to assign each line to a specific cesium site.
The spectra in Fig. 1A(a) and A(c) for H//b outside theplateau show a characteristic double-horn type line shapewith a continuum of finite intensity between two peaks.
Generally, such line shape is a signature of an incommensurate structure, in which the magnetic hyperfine fields at
nuclei have a sinusoidal modulation yielding a continuum.
The peaks of the spectra correspond to the extrema of themodulation. The fact that the spectra are asymmetric is
explained if the field is in the cycloidal spin plane. Since thespins should be more densely populated along the field
direction (Fig. 1[A](a)), we expect a distortion from purely
sinusoical hyperfine field modulation, resulting in an

Fig. 2. Temperature dependence of the spin-lattice relaxation rate at 14.5 T
inside (H//b) and outside (H//a) the plateau phase.

38

ISSP Activity Report 2002

asymmtric line shape.
Such a continuum is absent for the spectrum in theplateau region shown in Fig. 1[A](b). The spectrum consists
only of two nearly symmetric discrete peaks with the intensity ratio approximately 1:2 for both A and B-sites. This
result provides strong evidence that collinear up-up-downcommensurate spin structure is realized in the 1/3-plateau
phase.
In contrast, the spectra for the B-sites obtained for H//a
(Fig. 1[B]), where the magnetization plateau was notobserved, show symmetric double-horn type structure for all
fields, indicating persistence of the incommensurate structure for the entire field range. The symmetric line shape suggests cone-type spin structure shown in Fig. 1[B], where themodulation of the hyperfine field is purely sinusoidal. It
should be noted that, even though the cycloidal spin component is perpendicular to the field, anisotropic hyperfine
interaction generally produces parallel component of thehyperfine field. The A-sites, on the other hand, show a sharp
single peak, presumably because the anisotropy of thehyperfine interaction is not large enough.
The spin-lattice relaxation rates (1/T1) measured at
14.5 T inside (H//b) and outside (H//a) the plateau phase areplotted against T/TN (TN: the Neel temperature) in Fig. 2.
The relaxation rates decreases much more steeply for H//bthan for H//a, indicating different low lying excitation spectra for commensurate and incommensurate phases. In particular, the slow decrease for H//a at low temperatures is presumably due to gapless phase flctuations in the incommensurate structure.
Reference[1] H. Tanaka et al.: Phys. Rev. B67, 104431 (2003).
Authors
Y. Fujiia, T. Nakamuraa, M. Chibaa, H. Kikuchia, T. Gotob, K.
Kodama, S. Matsubara, and M. Takigawa
aDepartment of Applied Physics, Fukui University
bGraduate School of Human and Environmental Studies, Kyoto
University

Accurate Dynamic Structure Factor of
the Homogeneous Electron Liquid
H. Yasuhara and Y. Takada
The electron liquid, an assembly of N electrons embedded in a uniform positive background, has been studied toclarify the nature of electron correlation in metals, putting
aside the influence of the periodic ion potential. This simplified model poses us a tough problem, but after the struggles
lasting longer than half a century, accurate knowledge of its
almost all static properties is now acquired by a number ofsophisticated methods including quantum Monte Carlo simulations over the entire region of metallic densities
1.88<rs<5.6 where rs is the conventional density parameter.
As for dynamical properties, on the other hand, ourknowledge is still not enough in spite of all previous efforts
to go beyond the random-phase approximation (RPA) in an
attempt to explain the double-peak structure in the dynamical structure factor S(q,ω) observed in light metals like Al.
Among approximation schemes, the Baym-Kadanoff (BK)
conserving one formulated in terms of the full Green's function G is most suitable for the evaluation of S(q,ω).
Accuracy of the result depends critically on the choice of theFig. 1. Dynamical structure factor of the electron liquid at rs=5. The value
indicated by ωp is the plasmon energy at q=0. The excitonic effect manifests
itself in the structure indicated by a.

energy functional Φ [G], but the result will never become
exact, since no algorithm is known to give the exact Φ [G].
A conceptually different scheme is developed to obtain
the exact S(q,ω) [1]; instead of pursuing Φ[G], we pay attention to the exact functional relations between the self-energyΣ and the vertex function Γ, obeying the microscopic conservation law. In particular, Γ is determined by the BetheSalpeter equation with an irreducible electron-hole interaction given by the functional derivative, δΣ /δG. Starting froman arbitrary input, we iteratively revise both Σ and Γ simultaneously towards self-consistency through the relations,whereby the number of terms representing Σ generated inthis iterative process rapidly increases, eventually covering
all terms derivable from the exact Φ [G] when the self-consistency is achieved.
In a numerical algorithm, however, the functional differentiation δΣ /δG is not feasible. Thus we need to invent analternative scheme to revise Γ on a computer accurately andefficiently. Recently a physically motivated and accurateenough prescription is given for Γ [2], enabling us to obtain
the result of S(q,ω) [3] that is most accurate among all existing ones.

Fig. 2. Comparison between S(q,ω) of the electron liquid at rs=2.08 and theexperimental one for Al metal.

Throughout the metallic-density region, qualitative features of S(q,ω) remain the same; a typical example at rs=5 isgiven in Fig. 1. Besides a broad peak b located at almost thesame position in the RPA, there appears a clear shoulder aaccompanied by a steepened slope of the linear term inS(q,ω) for small ω. The peak b, being identified as “the center of gravity” of one-pair excitations, is transformed continuously into the plasmon peak as |q| decreases. The shoulder
a is well developed particularly for 1.4<|q|/pF <2 and theslope is surprisingly enhanced over the RPA value accordingly. These features imply inseparable coupling between
one- and multi-pair excitations in the one-pair excitation
region, attractive electron-hole multiple scattering (excitonic
effect) on the low-ω side of the one-pair region, and extra
contributions from multi-pair excitations outside of it.
Since accurate knowledge of S(q,ω) of the electron liquid is now available, we have compared it with the experimental one for Al, a metal regarded as most electron-liquidlike with rs=2.08, in order to see how the band effects modifies the actual structure of S(q,ω). The result of comparison
is shown in Fig. 2, which leads us to conclude that the electron-liquid model applies well to Al on the whole and especially so for ω <EF (~11eV). The discrepancy from themodel at higher ω is ascribed to the strong tight-binding
nature of unoccupied 3d and 4f bands in Al, leading to thestructure c in Fig. 2.
References[1] Y. Takada, Phys. Rev. B 52, 12708 (1995).
[2] Y. Takada, Phys. Rev. Lett. 87, 226402 (2001).
[3] Y. Takada and H. Yasuhara, Phys. Rev. Lett. 89, 216402 (2002).
Authors
Y. Takada and H. Yasuharaa
aInstitute for Materials Research, Tohoku University.

Magnetic Field-Induced Transition from a
Spin Jahn-Teller Antiferromagnet to a
3-1 Spin Ordered State in Geometrically
Frustrated Chromium Spinel
H. Ueda and T. Goto
It is well known that antiferromagnetism on the
pyrochlore lattice is a subject of strong frustration, giving
rise to highly degenerate magnetic ground states. To lift thegigantic degeneracy, the system often experiences a structural phase transition at low temperatures, which may beviewed as a spin Jahn-Teller effect. In the presence of magnetic field, however, the situation should be altered substantially. We might expect the formation of completely different spin ordering pattern produced by the interplay between
the frustration and the field induced spin alignment. This
spin state transition is likely accompanied with the structuralphase transition.
The CdCr2O4 oxide with the normal spinel structure is
one of the best defined spin Jahn-Teller systems together
with ZnCr2O4. A magnetic ordering in CdCr2O4 is marginally achieved by experiencing a structural transition fromcubic to tetragonal at 7.8 K. From the high temperature susceptibility, the Weiss temperature Θ is estimated to be-70 K. For the chromium ion with S=3/2, a magnetic field of
1 T corresponds to a temperature of 2 K. This implies thatthe energy scale of magnetic interaction in CdCr2O4 is com-

ISSP Activity Report 2002

39

Teller) transition. It should be emphasized that even above
the antiferromagnetic transition temperature, the first-ordertransition to the 3-1 state can clearly be observed around
30 T. Eventually above 10 K, the transition becomes broadand hardly identified. These results can be summarized visually as a H-T phase diagram in the inset of Fig. 1.
In summary, we found for the first time a 1/2 magnetization plateau in the S=3/2 Heisenberg pyrochlore antiferromagnet CdCr2O4. This spin version of a 3-1 charge ordering
recently found in AlV2O4 implies that the 3-1 ordering isquite universal in the pyrochlore lattice.

Fig. 1. Temperature dependence of the magnetization curve of CdCr2O4 forthe [111] direction. At low temperatures, a metamagnetic step at 28 T with apreceding plateau region is observed. A clear hysteresis behavior indicatesfirst-order transition. Although the step feature becomes broad with increasing temperature, it should be noted that the transition takes place above TN =7.8 K. The inset shows the H-T phase diagram up to 46 T.

parable to that of an experimentally achievable magnetic
field of several tens Tesla. Taking the advantage of relatively small magnetic interaction, we explored field-induced
phase transitions using pulsed high magnetic fields at ISSP.
We found a novel metamagnetic transition in CdCr2O4.
The magnetization curve for 1.8 K shows a discontinuous
jump around 28 T, followed by a magnetization plateau asshown in Fig. 1. The magnetization jump shows a hysteresis, indicating that it represents a first-order transition. Thistransition is accompanied by a jump of the magnetostriction. Considering the absence of spin-orbit coupling, thisrelatively large magnetostriction is surprising. We believethat this implies a strong spin-lattice coupling enhanced by afrustration.
The magnetic moment at the plateau is 1.5 µB/Cr3+,
which is exactly one half of the full moment of Cr3+ (S=3/2). One half plateau can be naturally understood by considering three up and one down configuration of four spins
on each tetrahedron, which may be considered as three
dimensional analogue of the 1/3 magnetization plateau intriangular antiferromagnets. There are two possible spin
structures. One has a rombohedral symmetry (R3m), in
which ferromagnetic kagomé and triangular layers are antiferromagnetically stacked along the [111] direction, as
shown in Fig. 2. The other has a cubic symmetry (P4332 orP4132) with down spins occupying the next nearest site.
The temperature dependence of the novel field-induced
transition was measured. In low fields, a discontinuouschange of the slope is clearly observed between 7 K and 8
K, which corresponds to the antiferromagnetic (spin Jahn-

Fig. 2. Two possible configurations in the plateau phase. Red circles correspond to up-spins and blue circles to down-spins. The left structure is cubic(P4332) and the right one is rhonbohedral (R3m).

40

ISSP Activity Report 2002

Authors
H. Uedaa, H. A. Katoria, H. Takagia, H. Mitamura, T. Goto
aRIKEN (The Institute of Physical and Chemical Research)

Superconductivity in Lithium UnderHigh Pressure
K. Shimizu and T.Yagi
In light elements, it is expected that superconductivity
occurs at high temperature. For example, in case of hydrogen, the transition temperature above room temperature has
been predicted [1], if it is compressed high enough andtransformed into metallic phase. Expected transition pressure of hydrogen into metallic phase, however, is too high toachieve using current high pressure experimental techniques. At ambient condition, lithium is the lightest metal of
all the elements and superconductivity at lower pressures are
expected. Previous electrical resistance measurements onlithium under high-pressure and low-temperature reported adrop of resistance at around 7 K under pressure [2], which
was proposed to be the onset of superconductivity.
However, because of the experimental difficulty to confine
lithium in a sample chamber of high pressure vessel, no confirmation was made since then. In the present study, we
have made a small pit at the top of the diamond-anvil apparatus, as shown in Fig. 1, which works as a sample chamber.
Because of the extreme hardness of diamond, such machining was difficult but by using a focused ultraviolet beamfrom pulsed KrF-excimer laser, wavelength 248 nm, we
could make such a pit. Lithium was successfully confined inthis pit and the electrical resistance was measured up to 48
GPa [3]. Normal metallic behavior was observed until thepressure was raised up to 30 GPa. When the pressure wasFig. 1. A photograph of a pit prepared at the top face of diamond anvil. The
size of the pit is 50 µm in diameter and 7 µm deep, on the 300-µm pressure
surface of the synthetic type Ib diamond anvil. The pit was prepared by afocused ultraviolet beam from pulsed KrF-excimer laser.

Fig. 2. Some examples of the electrical resistance of lithium measured attemperatures below 50 K. In this series of experiment, the pressure waschanged at 4 K and the increment of the resistance during compression was
negligible. The observed onset temperature of the drop shifted to higher temperature with increasing pressure, and reached to 20 K at 48 GPa.

increased further above 30 GPa, a drop of resistance wasobserved at around 7 K, as shown in Fig. 2, and the onset
temperature of the drop sifted to higher temperature withincreasing pressure. It has reached to 20 K at 48 GPa. The
effect of magnetic fields on the behavior of the resistancedrop was also measured, from which we could conclude that
this drop of resistance is due to the onset of superconductivity of lithium.
In this study we showed that lithium becomes superconducting at pressures greater than 30 GPa, with a pressure
dependent transition temperature (Tc) of 20 K at 48 GPa.
This is the highest observed Tc of any element; it confirms
the expectation that elements with low atomic numbers will
have high transition temperatures, and suggests that metallic
hydrogen will have a very high Tc. According to theoreticalpredictions on lithium, we may be able to achieve a Tc higher than 20 K on further compression and further studies are
now in progress.
References[1] C.F. Richardson and N.W. Ashcorft, Phys. Rev. Lett. 78, 118(1997).
[2] T. H. Lin and K.J. Dunn, Phys. Rev. B33, 807 (1986).
[3] K. Shimizu, H. Ishikawa, D. Takao, T. Yagi, and K. Amaya,
Nature, 419, 597(2002).

Fig. 1. Temperature dependence of resistance measured along the a-axis
under pressure in ZrTe3. A humped resistance anomaly is due to the CDW
transition.

known as linear chain compounds and it undergoes a CDW
state near 63 K and a superconducting state at ca. 2 K [1].
However, the properties of CDW and superconductivity of
ZrTe3 are largely different from those of typical MX3 suchas NbSe3 and TaS3; the CDW nesting vector has no component of the chain-axis direction and the superconductivity is
not of bulk nature but filamentary. These features of ZrTe3
lead us to an interest whether competition between the
superconductivity and the CDW is explained by the Fermi
surface nesting. We investigated the pressure effect of CDW
and superconductivity in ZrTe3 by measuring the electricalresistance down to 1.2 K under pressures up 0.6 Gpa using aclamp type piston-cylinder.
Fig. 1 shows the temperature dependence of the resistance along the a-axis between 20 K and 90 K under pressure[2]. At ambient pressure the resistance exhibits a humped
anomaly near TCDW=63 K. As pressure increases, TCDW anda magnitude of the resistance anomaly increase largely. Thisshows that CDW of ZrTe3 is significantly enhanced underpressure.
Fig. 2 shows the temperature dependence of resistancenear the superconducting transition under pressure. The
transition width is broad because of the filamentary natureof superconductivity. We defined Tc as the temperature corresponding to the zero resistance. Tc decreases significantly

Authors

K. Shimizua, H. Ishikawaa, D. Takaoa, T. Yagi, and K. Amayaa
aOsaka University

Unusual Pressure Effects on CDW andSuperconductivity in ZrTe3
K. Yamaya and Y. Uwatoko
In low-dimensional electron systems, there exist a variety of ground states such as charge-density-wave, spin-density-wave (CDW, SDW), and superconductivity. On investigating their coexistence or competition between them, theapplication of pressure has been used as a powerful tool.
Pressure-induced suppression of C(S)DW and enhancementof superconductivity are understood basically by change in anesting effect of the Fermi surface under pressure. ZrTe3 is
one of transition-metal trichalcogenides MX3 that is wellFig. 2. Temperature dependence of resistance measured along the a-axis
below 9 K under pressure. The superconducting transition width is broad,which can be represented well as the one-dimensional fluctuation even underpressure [3].

ISSP Activity Report 200241

with increasing pressure, showing the strong suppression of
the superconductivity under pressure [3].
Contrary to the usual pressure effect on competition
between CDW and superconductivity, we found pressureinduced enhancement of CDW and suppression of superconductivity in ZrTe3. This suggests that competition between
the superconductivity and the CDW is not simply explainedby the nesting effect of the Fermi surface, but other origin isneeded. Recent experiment of photoemission spectroscopyshows the CDW pseudogap formation growing from ~280 K[4]. The relationship between the pressure-enhanced CDW
and the CDW pseudogap formation is expected, although
yet inexplicable. Measurements under higher pressure areneeded.
References[1] S. Takahashi, T. Sambongi and S. Okada, J. de Phys., 44, C3-1733(1983).
[2] K. Yamaya, M. Yoneda, S. Yasuzuka, Y. Okajima, and S. Tanda,
J. Phys.: Condens. Matter, 14, 10767 (2002).
[3] K. Igarashi, S. Yasuzuka, K. Inagaki, S. Tanda, Y. Okajima, M.
Hedo, Y. Uwatoko, and K. Yamaya, J. de Phys. IV, 12, 97 (2002).
[4] T.Yokoya (private communication).
Authors
M. Yonetaa, S. Yasuzukaa, K. Igarashia, Y. Okajimab, K. Inagakia, S.
Tandaa, N. Hedo, Y. Uwatoko and K. Yamayaa
aDept. Appl. Phys. Hokkaido University
bAsahikawa National College of Technology.

Superconductivity at 14.2K in Layered
Organic Under Extremely High Pressure
H. Taniguchi, M. Hedo, Y. Uwatoko
Since the pressure, in general, weakens the electron correlation, even stiffly localized electrons in the Mott insulator
are expected to itinerate eventually under high pressure.
Upon this concept, we have picked up the molecular-based
Mott insulator, β’-(BEDT-TTF)2ICl2 [1], among manyorganic systems and tried to metallize it by application ofpressure, motivated by the fact that novel superconductivity
was often behind the insulating phase. Because the insulating nature of β’-(BEDT-TTF)2ICl2 is very strong, the pressure range of 0-2 GPa, which can be achieved by the widely-used piston-cylinder-type pressure cell, is not sufficientfor the present requirement. Then we adopt the cubic anvilpress [1], which makes it possible to measure the resistivity
under high pressure in the range of 2.0-10.0 GPa. Although
there are only a few studies [2,3], on the BEDT-TTF-based
complex under such extreme pressure, the resistivity of thepresent salt has been successfully measured up to 9.4 GPa
with good reproducibility.
Figure 1 shows the logarithmic resistivity of the β’(BEDT-TTF)2ICl2 as a function of temperature for variouspressures. The insulating behavior is gradually suppressedwith increasing pressure. Around 6.5 GPa, the metallic temperature variation appears in the high-temperature range followed by the low-temperature semiconducting behavior. At
almost the same time, a sharp peak shows up in the lowtemperature range. This peak is rapidly suppressed by further elevated pressure with gradual increase of the peak temperature. Finally, the clear superconducting transition withvanishing resistivity emerges below the normal metallic
state. Detailed characterization of the pressure-dependenceof the present superconductivity confirms that Tc reaches a

42

ISSP Activity Report 2002

Fig. 1. Resistivity of β’-(BEDT-TTF)2ICl2 salt as functions of temperatureand pressure.

maximum value, 14.2 K (onset), at 8.2 GPa (the inset). Thisis the highest Tc among the organics known to date.
We have constructed the pressure-temperature phase diagram of β’-(BEDT-TTF)2ICl2 salt through this study, as
shown in the Fig.2. The superconducting phase (S) just borders on the insulating phase (I). This feather suggests thatthe appearance of the present supercondcutuvity originatesfrom unconventional mechanism, as is the case with otherhighly correlated electron systems. Further researches are
required to clarify this issue.
References[1] N. Mori et al., JJAP Series No. 8, p. 182.
[2] K. Murata et al., Synth. Met. 103, 1891(1999).
[3] M. Miyashita et al., Physica C in press.
Principle Publication and Authors
H. Taniguchia, M. Miyashitaa, K. Uchiyamaa, K. Sotoha, N. Moria, H.
Okamotob, K. Miyagawac, K. Kanodac, M. Hedo and Y. Uwatoko, J.
Phys. Soc. Jpn. 72, 468 (2003).

Fig.2. Pressure-temperature phase diagram of β’-(BEDT-TTF)2ICl2. Metallic(M), insulating (I), and superconducting (S) phases are shown. TN of antiferromagnetic ordering has been determined only for ambient pressure.

aFaculty of Science, Saitama University
bFaculty of medicine, Kanazawa University
cDepartment of applied physics, University of Tokyo

Novel Antiferromagnetism in Mixed
Valence System YbMn2Ge2
T. Fujiwara and Y. Uwatoko
The ternary intermetallic compounds RMn2Ge2 crystallize in the tetragonal ThCr2Si2 type structure and their magnetic characteristics are dominated by the Mn 3d−Mn 3d
magnetic interactions. YbMn2Ge2 with unstable 4f electronstates shows a quite unique antiferromagnetism. As is shownin a P−T phase diagram (Fig.1), the Néel temperatures, TN1
and TN2, simultaneously exhibit a minimum and maximum
at ~1.25 GPa, respectively [1]. This indicates that a magnetic structural change occurs at Pc ~ 1.25 GPa and AFM I
state competes with AFM II state in YbMn2Ge2. Such acompetition behavior has not been found in other RMn2Ge2compounds being in static R3+ ionic states so far. These suggest that there is a strong correlation between the valence
instability of the Yb ion and the Mn 3d−Mn 3d magnetic
interactions. Thus, we investigated a pressure dependence ofa valence of Yb ionic state by X-ray absorption spectroscopy (XAS) measurements.
Figure 2 shows the normalized XAS spectra near the Yb
LIII threshold of YbMn2Ge2 under various pressures at 300
K. In the spectra at 0 and 0.59 GPa, we can recognize anapparent dual peaked edge structure which is typical featurein mixed valence systems. With applying pressure, the LIII
edge spectra of this system drastically change, indicatingthat the mean valence of Yb ion relatively varies toward thetrivalent state. These spectra can be interpreted as the superposition of two LIII white lines. We can obtain the fractional
occupation of 4f configurations from the intensity ratio of
the two LIII white lines. In order to estimate the Yb mean
valence, all the normalized spectra were analyzed in thestandard procedure by fitting with two subspectra which are
attributed to the Yb2+ and Yb3+ final states with the electronic configurations of (2p5 4f14 5d*) and (2p5 4f13 5d*), respectively, where each subspectrum consists of a Lorentzian andan arctangent function [2]. Consequently, the Yb mean

Fig. 2. X-ray absorption spectra near the Yb LIII threshold at 300 K undervarious pressures in YbMn2Ge2. The estimated Yb mean valence is plotted asa function of pressure in the inset

valence at ambient pressure was estimated to be ~ 2.4. This
indicates that YbMn2Ge2 is a typical mixed valence system.
The estimated Yb mean valence is plotted as a function ofpressure in an inset of Fig. 2. Here, the solid lines are guideto the eye for a variation of the Yb mean valence upon pressurization and the bluish broken line represents the criticalpressure Pc ~ 1.25 GPa which was estimated from the magnetization measurements under high pressures. It can beclearly seen that the Yb mean valence abruptly changes
around 0.9 ~ 1.25 GPa. Therefore, we can conclude that thepressure induced phase transition at Pc ~ 1.25 GPa originates in the abrupt change of Yb valence near the Pc. These
results are direct evidence that the instability of Yb 4f electrons state much affect on the Mn 3d−Mn 3d dominant interactions in RMn2Ge2 compounds as shown in Fig.1.
References[1] T. Fujiwara, H. Fujii, Y. Uwatoko, K. Koyama, M. Motokawa andT. Shigeoka, Acta Physica Pol B. 34, 1541 (2003).
[2] L. M. Falicov, W. Hanke and M. B. Maple. (Eds.), Valence fluctuations in Solids, North-Holland, Amsterdam, 1981.
Authors
T. Fujiwaraa, H. Fujiia and Y. Uwatoko
aFaculty of Integrated Arts and Sciences, Hiroshima University.

Vortex and Texture in Rotating Superfluid
3He
O. Ishikawa, T. Mizusaki and M. Kubota

Fig. 1. P−T phase diagram of YbMn2Ge2.

Texture is one of the crucial subjects in studying superfluid 3He. The texture is the configuration of internal freedom of condensation in spin space and in momentum space,
where the d-vector and l-vector are the order parameters representing such freedom, respectively. The configuration ofvectors are determined by several external conditions suchas magnetic field, boundary, flow field etc.. The energy corresponding to such a condition and the internal dipole energy compete each other and make a textural pattern in thetwo vector fields. Sometimes texture includes a defect in thecondensation state as a result of competition.
Recently three types of texture were found in narrowcylinders with 100 µm radius in A phase. Nuclear Magnetic
Resonance (NMR) technique is employed to identify each

ISSP Activity Report 2002

43

type of texture and it became evident that rotation of thecryostat which holds the sample cylinders is an important
external condition to do so, especially up to the world fastest
speed of 6.28 rad/sec at a constant temperature during thewhole measurement[2].
The radius of a long and narrow cylindrical sample wasabout ten times larger than the dipole coherence length so
any suppression of the order parameter is not expected. But
the boundary restriction on l-vector field strongly produces
an effect on the overall texture in the cell, which is definitely different from that of bulk liquid.
Figure 1 shows three NMR absorption spectra corresponding to three types of texture, observed at T/Tc=0.75
right after it was cooled through Tc from normal phase andat Ω=0 rad/sec, where Ω is the angular velocity of the rotating cryostat. Both A and B types of texture were observed
when the liquid was cooled slowly through Tc from normal
phase by cooling rate of 1 µK/min. The difference between
A and B is due to the external condition of the magnetic
field and the rotational direction while going through Tc.
Type A texture is found under the rotation at Ω=+2 rad/sec
and the magnetic field H=-22mT. On the other hand, type B
texture is formed under the same rotation but the opposite
magnetic field (Ω=+2 rad/sec, H=+22 mT). Type C texture
was observed when the liquid was cooled as fast as 10µK/min, ten times faster than for type A and B. This type C
texture did not depend on the external condition of the magnetic field and the rotation through Tc. The creation mechanism of type C is not clear. The large intensity of satellite
peak denoted by arrow may be due to the defect in texture
along the sample axis.
The absorption spectra for type A and B are changed byrotating the cryostat, showing the appearance and disappearance of the satellite signal and the change of main peak overthe critical angular velocity Ωn and under another one Ωa,respectively. Such a hysteresis is attributed to the quantum
vortex in the cell. Assuming a single vortex in the sample
liquid, the quantum number of circulation is just 3. This
integer is representing a macroscopic quantum phenomena
but 3 is a curious number, because the continuous vortex in
A phase has the quantum number of 2. Between +/-Ωn theintensity of main peak changed a little by rotation. Thismeans that each type A and B texture has an angularmomentum to couple with the rotation even in this rotating
speed. But it is evident to any one that the behavior of type
A and B is very different from each other (Fig.2). So theFig. 1. NMR absorption spectra for Ω=0 at T/Tc=0.75 as a function of frequency shift from the Larmor frequency. Spectra for 3 textures labeled by adotted line for A, a dashed line for B and a solid line C are shown.

44

ISSP Activity Report 2002

Fig. 2. NMR absorption of the main peak as a function of rotation speed Ωduring acceleration and deceleration cycle. The condition of cooling the sample through Tc are : (a) (+2 rad/sec, -22 mT), (b) (+2 rad/sec, +22 mT), (c) (-2
rad/sec, +22 mT), (d) (-2 rad/sec, -22 mT). The spectra (a) and (c) corresponds to type A texture and (b) and (d) to type B. Arrows indicate the direction of taking data and vertical lines are Ωn and Ωa for type A.

types A and B texture have different configurations of l-vector possessing the same angular momentum which may
explain the same critical angular velocity Ωa for vortex disappearance in both types of texture.
We believe that we are starting up a new field of superfluidity study where variety of intenal freedom of Cooper
pairs plays interesting new phenomena.
References[1] R. Ishiguro, M.Yamashita, O.Ishikawa, el al., Physica B329-333,
66(2003).
[2] M. Kubota, el al., Physica B329-333, Part1 1577(2003).
Authors
O. Ishikawaa and M. Kubota.
aOsaka City University

ISSP WorkShop (April 2002〜March 2003)
1. Frustrated magnetism and novel properties

June 19 ~ 21, 2002

Frustration is ubiquitous in nature. It describes the situation where several optimization conditions compete witheach other and are incompatible. Under frustration, the system tends to be unstable and is often subject to strong fluctuation effects, which could give rise to many interesting novel phenomena not encountered in standard unfrustrated
systems. In the ISSP workshop, we concentrated on frustrated magnetism and related novel phenomena in condensed
matter physics. The topics covered were fairly wide, from the nature of various novel magnetic phase transitions andordered states of frustrated magnets, to novel transport and electronic properties of metallic frustrated systems.
Mentioning some of the topics hotly discussed, magnetic ordering of kagome and pyrochlore magnets including spin
ice, quantum spin ordering of geometrically frustrated magnets, nature of the ordering of chirality and its effect ontransport properties such anomalous Hall effect, geometrical frustration and strongly correlated electron systems,
ordering and off-equilibrium dynamics of spin glasses, etc.

2. New developments in glass physics

July 10 ~ 12, 2002

The glass forming process is a transition from liquids to solids in non-equilibrium systems and is a phenomenon
totally different from crystallization. Recent extensive studies in Japan and around the world have revealed that the
dynamical and thermodynamic characteristics of the glass forming process could be understood in a unifying manneron the basis of the energy landscape picture. In this workshop, latest results from experimental, theoretical and computational studies were presented with emphasis on the glass transition and the properties of glasses. From the intensive
discussions following each oral presentation and in the poster session, a new direction of the research on glass physics
has emerged, which will be pursued as some joint efforts.

3. High field science-present status and perspectives

October 8 ~ 9, 2002

The purpose of this workshop is to establish near future perspectives on high field science in Japan, especially inthe field of condensed matter physics. For this purpose, selected reviewers are invited to give overviews on importantfields of high field science. Topics included are superconductivity, semiconductor physics, quantum spin systems,
material processing, chemistry and various types of spectroscopy in high magnetic fields. In addition, several novel
topics on researches in high magnetic fields are shown. Examples of topics are THz spectroscopy, quantum plateau,quantum phase transition and novel strongly correlated systems in high magnetic fields. The present status of major
high field facilities and independent high field laboratories are also reported. The final session is devoted for the establishment of High Magnetic Field Forum of Japan. The first meeting of the forum is successfully made and the organizing committee is selected (for details, see http://www.issp.u-tokyo.ac.jp/contents/others/himag-forum/index.html).

4. Physics of friction

October 23 ~ 25, 2002

Friction is one of the most familiar physical phenomena and its research has long history due to its importance.
The fundamental mechanism of friction is, however, not well understood still now. Recently many new experimental
techniques, such as surface controlling technique, Ultra High Vacuum technique, Atomic Force Microscope, Frictional
Force Microscope, Quartz Crystal Microbalance technique, Surface Force Apparatus and so on, enable us to investigate frictional phenomena from a modern point of view along with the progress of theoretical and numerical studies.
The physics of sliding friction at solid surface has strong relation with many problems in conventional condensed matter physics, i.e., vortex and density wave dynamics, etc. In this workshop we had about 50 talks and discussed lively
recent progress of "physics of friction" in various systems for 3 days.

5. Computational physics in condensed matter research

November 6 ~ 8, 2002

Recent developments of the field, achieved mostly by making use of the supercomputer system in the
Supercomputer Center at ISSP, were discussed in the workshop. Particularly emphasized were new computational
methods which, combined with large-scale calculations, enable us to analyze various cooperative phenomena in condensed matters. They are time-dependent density functional molecular dynamics simulations, first-principles
approaches for strongly correlated systems and for transition-metal surfaces, the path integral renormalization groupmethod, the non-equilibrium relaxation method, the probability-changing cluster algorithm, and so on. In a special
session of the workshop, we also discussed the present status of, and future requirements for the ISSP supercomputer
system, which is placed at the service of general researchers of condensed matter physics in Japan.

ISSP Activity Report 2002

45

6. New materials and new functions in molecular conductors

November 25 ~ 27, 2002

Cooperation of chemistry and physics has been an important impetus in the research field of molecular conductors.
Recently, record high Tc of organic superconductors has been raised to 14.2 K by the application of extremely highpressure. Superconductivity is realized in newly designed donor molecules, which include novel superconductors withenhanced electron correlation and those with incommensurate structures. In addition, new materials have developed
characteristic new physics; examples are structure-property correlation such as the universal phase diagram, chargeorder, large uniaxial strain effects, and field-induced superconductivity and giant magnetoresistance in πd-systems.
Recent ideas coming from device physics and nano science are also giving large impacts on this field. In this workshop, specialists in this research field, together with researchers who are interested in molecular conductors from thenew point of view, provide a survey of the recent research, and discuss the development aiming at new functions.

7. Materials researches in the 21 century using new-generation VUX / SX light sources
December 13 ~ 14, 2002
In relation to the new VUV / SX light source project supported by all users, recent hot results and new researchpossibilities using synchrotron radiation in solid-state science and technology were presented by actively working
young researchers. The workshop attracted over 90 scientists from universities, national institutes and private companies. The workshop covered wide variety of spectroscopic studies on nanostructures, magnetic ultrathin films, superconducting materials, organic-device related materials, surface dynamics, and surface chemistry. Topics of new experimental techniques and instrumentations related to these studies were also included. In addition to these, a promisingidea to obtain ultrashort synchrotron-radiation pulse was introduced by accelerator group. Very exciting discussions
were made throughout the workshop. Discussions clearly indicated that spectromicroscopy, photoelectron emission
microscopy (PEEM), time-resolved spectroscopy and very high-resolution spectroscopy coupled with the new generation VUV / SX light source with high brilliance and polarization tunability will undoubtedly open new sciences inthese fields.

8. Manipulation and assembly of atoms and molecules based on nanomechanics
January 20 ~ 21, 2003
The atomic force microscope (AFM) is a unique microscope based on a nanomechanical method, which has the following characteristics; (1) it has true atomic resolution, (2) it can measure atomic force (so-called atomic force spectroscopy), (3) it can observe even insulators, and (4) it can measure mechanical responses such as elastic deformation.
Indeed, during the last few years, the noncontact AFM (NC-AFM) achieved the true atomic resolution on various surfaces, the three-dimensional mapping of atomic force, discrimination of atomic force mechanisms, discrimination of
atom species on sample surfaces, control of atomic force between the tip and sample atoms, control of atom position on
sample surfaces, and mechanical atom manipulation. In this workshop, recent activities on atoms, molecules andbiopolymers based on the nanomechanical method are reported and we discussed how to approach to manipulate andthen assemble atoms and molecules into nanostructures both experimentally and theoretically.

9. Present and future of research in high magnetic fields

May 29, 2002

The use of high magnetic fields for material research is rapidly developing nationally and internationally in thesedays as the magnet technology becomes advanced. In the United States and Europe, large-scale facilities to generatehigh magnetic fields are being built one after another under government projects. Considering such situation, we need
immediately to make closer cooperative relationship among research groups in Japan in order to strengthen our
research system and create outstanding results which can lead the world of high magnetic field again. Therefore, magnetic field researchers in Japan agreed to establish "The High Magnetic Field Forum of Japan" to promote study ofhigh magnetic field physics in Japan. In the process of discussing the forum, we found that it might be necessary toconstruct a long pulse magnet facility as a facility for professional joint research. In this workshop, leading people invarious fields of solid state physics made their own proposals for the possibility of science that a new facility enables
us to pursuit for the first time.

46

ISSP Activity Report 2002

10. DSC workshop

June 12 ~ 13, 2002

The Materials Design and Characterization Laboratory (MDCL) in ISSP aims to promote materials science with anemphasis on the "DSC cycle" where DSC is integration of three functions, Design, Synthesis and Characterization.
Recent activities on various topics of materials development, including the results obtained by User Programs, were
presented as 28 talks and discussed in this workshop. A new direction of the research and a future plan of MDCL werealso discussed. The workshop was very successful with active discussions among more than 50 participants.

11. Research prospects on atom- and molecular- spectroscopy and biology using VUX / SX highbrilliant light source
September 17 ~ 18, 2002
In relation to the new VUV / SX light source (Super SOR) project, recent hot results and new prospects using synchrotron radiation in atom- and molecular spectroscopy and biology were presented by actively working young
researchers. The workshop attracted 37 scientists from universities, national institutes and private companies. The
workshop covered spectroscopic studies of atoms, molecules and clusters, soft-X-ray imaging, and radiation effect tobio-matters. The status of the project as well as the design of the beamline monochromators were also introduced. Mostof the proposals were challenging and interesting. Especially, the new optical mount for the soft-X-ray emission spectroscopy monochromator by Dr. Hatsui (IMS) was very impressive. It was noticed further that the demands to themicro-beam or imaging techniques using Super SOR is very high.

12. Future plan on neutron scattering sciences in soft matter physics

October 25 ~ 26, 2002

Neutron scattering technique has been one of the most powerful tools for nanostructure investigations as well as
molecular dynamics studies on soft matter physics. The year of 2001 was the last of a ten-year contract of the Neutron
Scattering Laboratory, ISSP, and for renewal starting from 2002. On this occasion, a workshop on future directions ofsoft matter physics with neutron scattering techniques was held on Oct. 25 and 26, 2002, at Neutron Scattering
Laboratory, Tokai. More than 40 participants attended and discussed on various themes, including (1) today and futureof neutron sources and the guide hall of JRR-3M, (2) refurbishment and/or construction of the neutron spectrometers,(3) the relationship between the J-PARC Plan and JRR-3M, and (4) soft matter science and the amenity and laboratoryenvironments at Tokai. It was recognized that neutron scattering techniques would become more fundamental and key
tools for soft matter science. Hence, further financial and personnel support from the government and funding organizations would be strongly recommended.

13. Dr. Rohrer's JSPS award workshop III and ISSP international workshop  a role of physics
for nano science and technology February 17 ~ 18, 2003

Dr. Heinrich Rohrer, a Novel laureate in Physics for an invention of scanning tunneling microscopy, was awarded
by Japan Society for the Promotion of Science (JSPS) as a Prominent Scientist. Commemorating the award-winning, aworkshop has been held every half year with Dr. Rohrer as a honorary participant. This workshop, combined with an
ISSP international workshop, is the third one of the JSPS workshop series. Main theme of this workshop is nano science and technology, which Dr. Rohrer pioneered, and their physics sides was particularly discussed. Presented subjects included molecular excitation and manipulation, controlled cluster formation, nanotube technology, functional
one-dimensional structure, novel techniques for high-resolution AFM and ultrafast STM, Coulomb blockade andcoherence, and etc. With 14 talks including 2 invited talks from abroad, 34 posters and more than 100 participants, thediscussion at the workshop was very active and fruitful.

ISSP Activity Report 2002

47