Abstracts of Papers

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Department of Physics Engineering* nonmember
Unitarity in gauge symmetry breaking on orbifold. Y. Abe, N. Haba, Y. Higashide, K. Kobayashi, M. Matsunaga: Progress ofTheoretical Physics, 109, pp.831 - 842, 2003.
We study the unitarity bounds of the scattering amplitudes in the extra dimensional gauge theory where the gauge
symmetry is broken by the boundary condition. The estimation of the amplitude of the diagram including four massive gaugebosons in the external line shows the power behavior of the amplitude is canceled. The calculation will be done in the 5dimensional standard model and the SU(5) grand unified theory, whose 5th dimensional coordinate is compactified on S^1/Z_2.
The broken gauge theories through the orbifolding preserve the unitarity at high energies similarly to the broken gauge theories
where the gauge bosons obtain their masses through the Higgs mechanism. We show that the contributions of the Kaluza-Klein
states play the crucial rolls for conserving the unitarity.

Correlation Functions at Antiferroelectric Smectics by Means of Transfer Matrix Method, S. TANAKA* and M.
YAMASHITA: Mol. Cryst. Liq. Cryst. 398, pp. 45-56, 2003.
The mechanism of successive phase transitions occurring at antiferro-electric smectics is well described by ANNNI
model. Here the transfer matrix method is generalised so as to be applied to this model with long range interaction. The
correlation function is obtained, which shows oscillating behaviour with varying wave number due to the complex eigenvalueof transfer matrix. In the framework of this method the critical temperature of the model is estimated by replacing an intralayerinteraction by the molecular field.

Maier-Saupe Nematic Isotropic Phase Transition in the Presence of an External Field, M. Yamashita: Mol. Cryst. Liq. Cryst.
398, pp. 75-85, 2003.
The nematic-isotropic phase transition in an external field is studied in the frame of Maier-Saupe model, where a global
phase diagram including both cases of positive and negative susceptibility anisotropic is obtained. In the extreme case of
infinitely large negative anisotropy, the system is reduced to the classical XY model because the rotational degree of freedom isrestricted to lie in the plane perpendicular to the field, in which the second order phase transition occurs. The crossover of thedirectional degree of freedom between 3-dimension and 2-dimension is depicted. On the other hand, the critical point appears at
a certain strength of the positive anisotropy, beyond which the transition disappears. The theory can be applied to the phasetransition of very thin systems with homeotropic and planar anchorings.

Global Phase Diagram of Maier-Saupe Model and Inhomogeneity Due to Walls, M. Yamashita: J. Phys. Soc. Jpn. 72, pp.
1682-1688, 2003.
A global phase diagram of Maier-Saupe model for nematic-isotropic phase transition on the external field versus
temperature plane is obtained, where due to non-polar property of the system two sets of order parameters and the conjugate
fields are required to describe completely the phenomena. The phase diagram is argued in the context of a similarity of themodel to the three-state Potts model. Inhomogeneity at the thin system sandwiched by parallel walls is expressed in terms of aneffective external field, where effects due to homeotropic, homogeneous, planer and oblique anchoring walls are classified
systematically. A shift of the transition temperature together with the property of phase transition is explained systematically on
the basis of the phase diagram of bulk system, where the changes of the order of phase transition is related to a critical point anda tricritical one appearing in the phase diagram.

Ａ−88

Abstracts of Papers

Continuous Phase Change Mediated by an Unstable State at Freely Suspended Smectic Films, M. Yamashita: J. Phys. Soc. Jpn.
72, pp. 2421-2424, 2003
Phase transitions of freely suspended chiral smectic films exhibiting a first order phase transition in a bulk system arestudied in the framework of a phenomenological theory, in which such a widely observed finding that the surface layer orders at
a temperature higher than the bulk critical temperature is taken into account. While the inner portion of the film exhibits the firstorder phase transition at a temperature below that of the surface layer in the system of sufficient thickness, a continuous change
occurs for the system with a thickness smaller than a critical thickness. The mechanism of the continuous change is elucidated
on the basis of the phase diagram of the bulk system on the field versus temperature plane, where nonuniformity due to theordered surface layers is replaced by an effective field and the high-temperature phase is connected

Unambiguous relationship between the Hubbard, t-J and d-p models in One-dimension based on the Luttinger liquid Theory,
Kazuhiro Sano and Yoshiaki Ono*: Physica C388-389., pp. 84-85, 2003.
We examine the one-dimensional (1D) d-p model in comparison with typical 1D models such as the 1D Hubbard
model and the 1D t-J model using the numerical diagonalization method combined with the Luttinger liquid theory. We
calculate the spin velocity vσ, the charge velocity vρ and the Luttinger liquid parameter Kρ for each model. Using theseparameters, a relationship between the models is obtained unambiguously. We find that the d-p model can be described by the
Hubbard model in the wide parameter region, while it can be described by the t-J model only in the strong coupling limit.

Ferromagnetism and Superconductivity in the Multi-orbital Hubbard Model: Hund's Rule Coupling versus Crystal-Field
Splitting, Kazuhiro Sano and Yoshiaki Ono*: J. Phys. Soc. Jpn, 72, pp. 1847-1850, 2003.
The multi-orbital Hubbard model in one dimension is studied using the numerical diagonalization method. Due to theeffect of crystal-field splitting ∆, the fully polarized ferromagnetism, which is observed in the strong coupling regime, becomes
unstable against the partially polarized ferromagnetism when Hund's rule coupling J is smaller than a certain critical value oforder of ∆. In the vicinity of the partially polarized ferromagnetism, the orbital fluctuation develops due to the competition
between Hund's rule coupling and crystal-field splitting. The superconducting phase with the Luttinger liquid parameter Kρ isobserved for the singlet ground state in this region.

Nonlinear Sigma model method for the J1-J2 Heisenberg model: disordered ground state with plaquette symmetry, K. Takano,
Y. Kito, Y. Ono, K. Sano: Phys. Rev. Lett. 91, pp.197202-1-197202-4 , 2003.
A novel nonlinear model method is proposed for the two-dimensional J1-J2 model which is extended to include
plaquette-type distortion. The nonlinear model is properly derived without spoiling the original spin degrees of freedom. The
method shows that a single disordered phase continuously extends from a frustrated uniform regime to an unfrustrated distorted
regime. By the continuity and Oshikawa’s commensurability condition, the disordered ground states for the uniform J1-J2
model are plaquette states with fourfold degeneracy.

Abstracts of Papers

Ａ−89

Semigrand Canonical Monte Carlo Simulation with Gibbs-Duhem Integration Technique for Alloy Phase Diagram, Atsushi
MORI*, Brian B. LAIRD*, Yoshihiro KANGAWA*, Tomonori ITO and Akinori Koukitu*: Materials Physics and Mechanics,
6, pp.49 - 57, 2003.
Formulation is given for the Gibbs-Duhem integration (GDI) method in the semigrand canonical (SGC) ensemble, inwhich the total number of particles N is fixed with the specified chemical potential differences between species ∆µ.
Demonstration of the SGC Monte Carlo simulation with the GDI technique is given for a pseudo-binary semiconductor alloy
InxGa1-xN.

Semigrand Canonical Monte Carlo Simulation with Gibbs-Duhem Integration Technique: Formulation for Alloy Phase
Diagrams and Attempt on InxGa1-xN/GaN, Atsushi MORI*, Brian B. LAIRD*, Yoshihiro KANGAWA*, Tomonori ITO andAkinori KOUKITU*: Russian Journal of Physical Chemistry, 77, pp.521-529, 2003.
We give formulation for the Gibbs-Duhem integration (GDI) method in the semigrand canonical (SGC) ensemble, inwhich the total number of particles N is fixed with the specified chemical potential differences between species ∆µ. For a binary
system in the isobaric SGC ensemble, the equation to be integrated in the T- ∆µ plane is d(∆µ eq)/dT=-∆h/T∆x, where ∆µ eq gives
II I∆µ at equilibrium between phases I and II at temperature T, ∆h represents enthalpy difference h -h , and ∆x represents the
I II
composition differences x -x . Attempting application of SGC Monte Carlo simulation with the GDI technique to a
pseudobinary semiconductor alloy InxGa1-xN is presented, the preliminary result of which reflects the asymmetric nature of anexcess energy curve calculated on the basis of an empirical interatomic potential used in the present Monte Carlo simulation.

Intra-Atomic Noncollinear Magnetism and the Magnetic Structures of Antiferromagnetic FeMn, Kohji NAKAMURA,
Tomonori ITO, A. J. FREEMAN*, Lieping ZHONG* and J. Fernandez-de-CASTRO*: Physical Review B, 67, pp.
014405-1-4, 2003.
Both collinear and noncollinear magnetic structures of FeMn with L10 atomic ordering were determined fromtotal-energy full-potential linearized augmented plane-wave calculations incorporating noncollinear magnetism with no shape
approximation for the magnetization density. Different spin-density orientations for the different band states are observed on asmaller length scale inside an atom. The presence of the intra-atomic noncollinear magnetism enhances the stability of the 3Q
noncollinear magnetic structure, in which the magnetic moments align toward the center of the cell of four atoms, thus
becoming the lowest-energy state of the structures considered.

Enhancement of Magnetocrystalline Anisotropy in Ferromagnetic Fe Films by Intra-Atomic Noncollinear Magnetism, Kohji
NAKAMURA, Tomonori ITO, A. J. FREEMAN*, Lieping ZHONG* and J. Fernandez-de-CASTRO*: Physical Review B,
67, pp. 014420-1-6, 2003.
We generalize the full-potential linearized augmented plane-wave method with a single slab geometry in order to treat
noncollinear magnetism with no shape approximation for the magnetization, and apply this scheme investigate free-standing
Fe(001) monolayers with lattice constants matching those of fcc Ag(001) and Cu(001) substrates. Intra-atomic noncollinear
magnetism on a smaller length scale inside the atom is observed in the ferromagnetic state, and is found to enhance themagnetocrystalline anisotropy energy (by 17~20%) compared to values determined for their collinear magnetic state.

Ａ−90

Abstracts of Papers

First Principles Investigation of Domain Walls and Exchange Stiffness in Ferromagnetic Fe and Antiferromagnetic NiMn,
Kohji NAKAMURA, Tomonori ITO, A. J. FREEMAN*, Lieping ZHONG* and J. Fernandez-de-CASTRO*: Journal ofApplied Physics, 93, pp. 6879-6881, 2003.
We investigate the domain walls in ferromagnetic Fe and antiferromagnetic NiMn with the first principles full-potential
linearized augmented plane-wave method including intra-atomic noncollinear magnetism. In both cases, the self-consistent
results demonstrate that the magnetization changes continuously from one orientation to another as seen in a Bloch wall. The
formation energy of the domain wall significantly decreases when the wall thickness increases, which leads to an exchange
stiffness of 1.13×10-11J/m for Fe and 1.43×10-11J/m for NiMn. The predictions agree with those determined separately for Fefrom a phenomenological calculation

Curling Spin Density and Orbital Structures in a Magnetic Vortex Core of an Fe Quantum Dot, Kohji NAKAMURA,
Tomonori ITO and A. J. FREEMAN*: Physical Review B, 68, pp. 180404(R)-1-4, 2003.
First results of the spin and orbital structures in the vortex core of an Fe dot obtained using highly precise first principles
calculations that include intra-atomic noncollinear magnetism are reported. We demonstrate that a curling magnetic structure isstabilized within a 4 nm radius dot as inferred from spin-polarized scanning tunneling microscopy experiments in which thespin directions close to the center of the dot turn up along the perpendicular orientation to the curling plane-and also predict acomplicated curling intra-atomic noncollinear magnetism near the center in which the spin moments continuously cant incircular directions on a smaller length scale inside the atoms. Importantly, these rotation properties in the spin density couple tothe orbital motion and induce orbital moments oriented perpendicular to the curling plane, which is a first prediction ofquantum phenomena induced in the nanoscale vortex core.

Influence of lattice Constraint from InN and GaN Substrate on Relationship between Solid Composition of InxGa1-xN Film and
Input Mole Ratio during Molecular Beam Epitaxy, Yoshihiro KANGAWA*, Tomonori ITO, Yoshinao KUMAGAI*, Akinori
KOUKITU* and Norihito KAWAGUCHI*: Japanese Journal of Applied Physics, 42, pp. L95-L98, 2003.
Thermodynamic analyses were carried out to understand the influence of lattice constraint from InN and GaN
substrates on the relationship between solid composition x of InxGa1-xN films and input mole ratio RIn. The calculation results
suggest that a compositionally unstable region is found at the GaN-rich region for InGaN on InN at higher temperatures whilethat for INGaN on GaN can be seen at the InN-rich region. This is because the maximum enthalpy of mixing shifts towardx~0.10 for InGaN on InN and toward x~0.80 for InGaN on GaN compared with x~0.50 for stress-free InGaN.

Effect of Ni-Cu Substrates on Phase Selection of Hexagonal and Cubic Boron Nitride Thin Films, Shigeo KOTAKE, Takaya
HASEGAWA, Kazutaka KAMIYA, Yasuyuki SUZUKI, Takami MASUI*, Yoshihiro KANGAWA*, Kohji NAKAMURA
and Tomonori ITO: Applied Surface Science, 216, pp. 72-77, 2003.
The dependence of the phase selection of BN on the lattice parameter and the crystal structure of the substrate wasclarified. BN thin films were prepared by RF sputtering method on polycrystalline Ni-Cu complete solid solution alloy. Using
empirical potentials, the polytypes of BN thin films were systematically investigated by considering lattice constraint due tovarious interface atomic arrangements and orientations such as c-BN or h-Bn on cubic (001) or (111) substrates. From IR
spectrum, merely c-BN phase was observed from the specimen on Cu and Ni0.8-Cu0.2 alloy. Moreover, the empirical potential
calculations reveal that c-BN thin films on (001) substrates can be stabilized in the substrate lattice parameter of 3.2<a<4.4 Å.

Abstracts of Papers

Ａ−91

Thermodynamic Study on Compositional Instability of InGaN/GaN and InGaN/InN during MBE, Yoshihiro KANGAWA*,
Tomonori ITO, Yoshinao KUMAGAI* and Akinori KOUKITU*: Applied Surface Science, 216, pp. 453-457, 2003.
Thermodynamic analyses were carried out to understand the influence of lattice constraint from GaN and InN
substrates on relationship between solid composition x of InxGa1-xN films and input mole ratio RIn. The calculated results
suggest that a compositional unstable region is found at small RIn region for InGaN on InN while that for INGaN on GaN canbe seen at large RIn region at higher temperatures. This implies that InN-rich thin films are possible to form on InN substrate
though it is difficult to form on GaN substrate.

Systematic Theoretical Investigations of Miscibility in Si1-x-yGexCy Thin Films, Tomonori ITO, Kohji NAKAMURA, Yoshihiro
KANGAWA*, Kenji SHIRAISHI*, Akihito TAGUCHI* and Hiroyuki KAGESHIMA*: Applied Surface Science, 216, pp.
458-462, 2003.
Miscibility of C in Si1-x-yGexCy thin films is systematically investigated by using the empirical interatomic potentials.
The empirical potential approach is applied to calculate excess energies for Si1-x-yGexCy thin films incorporating interface lattice
constraint due to Si(001). In order to compare with experimental results, we employ the content values such as x=0.13, 0.22,
0.27, 0.31, 0.35, and y=0.019. The calculated results imply that the lattice constraint at the interface and Si-C interatomic bondformation dramatically reduce excess energies of Si1-x-yGexCy thin films by 20-30% of those in bulk state. Therefore, the lattice
constraint promotes C incorporation in Si1-x-yGexCy thin films. Furthermore, segregation phenomena of Ge and C atoms in
Si0.78Ge0.2C0.02 on Si(001) is clarified by Monte Carlo simulation taking into account surface and interface structures. The
simulated results reveal that Ge atoms segregate in the topmost layer and C atoms accumulate in the second layer.

An Empirical Potential Approach to Structural Stability of GaNxAs1-x, Takashi SUDA, Yoshihiro KANGAWA*, Kohji
NAKAMURA and Tomonori ITO: Journal of Crystal Growth, 258, pp. 277-282, 2003.
Thermodynamic stability of GaNxAs1-x including zinc blende (ZB) – wurtzite (W) structural stability and miscibility issystematically investigated based on a newly developed empirical potential, which incorporates electrostatic energies due tobond charges and ionic charges. Using the empirical potential, the system energies of W and ZB form are calculated for bulk
GaNxAs1-x over the entire concentration range. The calculated results predict that the structural phase transition from ZB to W
occurs at x~0.4, which differs from x~0.7 estimated by electrostatic energy contributions. The shift of the ZB-W structuraltransition concentration toward x~0.4 is clarified in terms of difference in bond length distribution between ZB- and
W-GaNxAs1-x. Based on these findings, the miscibility of GaNxAs1-x is discussed by excess energy calculations.

Atomic and Electronic Structure of Misfit Dislocations in GaSb/GaAs(001), Nori MIYAGISHIMA*, Takuya SHINODA*,
Ken SUZUKI*, Tadasuke KANEKO*, Kyozaburo TAKEDA*, Kenji SHIRAISHI* and Tomonori ITO: Phyisica B, 340-342,
pp. 1009-1012, 2003.
We investigated the atomic and electronic structures of the periodic misfit dislocations (MDs) found in
GaSb/GaAs(001). In order to determine the details of these structures, we carried out the first-principle total energy calculations.
The characteristic feature in the MDs is the appearance of the anion-anion or cation-cation bond in order to avoid the formationof dangling bonds. As a result, the dislocation core structure form five- and seven-membered rings. These MDs electronicallycause the impurity levels in the band gap. The individual MDs have the possibility to form one-dimensional electron- andhole-paths along the dislocation line.

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Abstracts of Papers

Superlattice Stacking Structure in InGaN Thin Film Pseudomorphic to GaN(0001) Substrate: Semigrand Canonical Monte
Carlo Simulation, Atsushi MORI*, Tomonori ITO, Yoshihiro KANGAWA*, Yoshinao KUMAGAI* and Akinori
KOUKITU*: Physica Status Solidi (c), 0, pp. 2486-2489, 2003.
Superlattice stacking structures in the Ga-rich branch of wurtzite InxGa1-xN/GaN were found using semigrand canonicalMonte Carlo simulations, which were performed aiming at the construction of the alloy phase diagram. Simulated systems
were InxGa1-xN thin films pseudomorphic to the GaN(0001) substrate. Continuing the simulations, we revealed that In-richlayers parallel to the substrate were formed in Ga-rich regions. At 800 K, traversing along the c direction GGGIGGGI…
superlattice-type stackings were more frequently observed, where G and I indicate the Ga-rich and In-rich layers, respectively.
As the temperature increased along the two-phase boundary the superlattice structure changes so that many In-rich layers were
included. The In content of the Ga-rich phase eventually exceeded 0.5 at a higher temperature such as 875 K.

Influence of Lattice Constraint from InN and GaN Substrate on Relationship between Input Mole Ratio and Solid Compositionof InGaN during MOVPE, Yoshihiro KANGAWA*, Tomonori ITO, Yoshinao KUMAGAI* and Akinori KOUKITU*:
Physica Status Solidi (c), 0, pp. 2575-2579, 2003.
Thermodynamic analyses incorporating the contribution of lattice constraint from the substrates were carried out tounderstand the relationship between input In mole ratio and solid composition of stress-free InGaN, InGaN on GaN and InGaN
on InN during metalorganic vapor phase epitaxy. The calculated results suggest that a compositionally unstable region is foundat the InN-rich region for InGaN on GaN at high temperatures, while that for InGaN on InN can be seen at the GaN-rich region
due to the lattice constraint from the substrate. These results imply that incorporating the contribution of lattice constraint is
indispensable to predict the thermodynamic properties of such materials.

Influence of Lattice Constraint from Substrate on Relationship between Input Mole Ratio and Solid Composition of InGaN
during MBE and MOVPE [in Japanese], Yoshihiro KANGAWA*, Tomonori ITO, Yoshinao KUMAGAI* and Akinori
KOUKITU*: Journal of the Japanese Association for Crystal Growth, 30, pp.104 - 110, 2003.
Thermodynamic analyses were performed to understand the influence of lattice constraint from InN and GaN
substrates on the relationship between solid composition x of InxGa1-xN films and input mole ratio RIn during molecular beam
epitaxy (MBE) and metalorganic vapor phase epitaxy (MOVPE). For the both growth methods, the calculation results suggestthat a compositionally unstable region is found at the InN-rich region for InGaN on GaN at higher temperatures while that for
InGaN on InN can be seen at GaN-rich region due to the lattice constraint from the substrate. Incase of the MOVPE, it is foundthat growth region of InGaN in the diagram related to V/III ratio and solid composition shrinks with increase of V/III ratio. Thisis because the H2 partial pressure produced by the decomposition of NH3 increase at high V/III ratio

Ab initio-Based Approach to Structural Stability of GaAs Surfaces [in Japanese], Yoshihiro KANGAWA*, Tomonori ITO,
Kenji SHIRAISHI*, Tadashi OHACHI and Akinori KOUKITU: Journal of the Surface Science Society of Japan, 24, pp.
642-647, 2003.
An ab initio-based approach was made to understand the influences of temperature and beam equivalent pressure(BEP) on the structural stability of GaAs surfaces. The theoretical approach incorporates free energy of vapor phase; therefore
we can calculate how structural stability of GaAs surfaces depends on the temperature and beam equivalent pressure. By thetheoretical investigations, temperature and BEP dependencies of the stability of GaAs(001)-(4x2) were predicted. The results
agree with experimental results, and feasibility of the theoretical approach was confirmed. Furthermore, the relative stability of
Ga adatom among the case of that on GaAs(001)-(2x4) and (11n)A (n=2, 3, 4) surfaces were studied.

Abstracts of Papers

Ａ−93First-principles Study of Reaction of Atomic Oxygen at SiO2/Si(100) Interface, Toru AKIYAMA and Hiroyuki
KAGESHIMA*: Proc. of the 26th International Conference on the Physics of Semiconductors, Edinburgh, 2003.
Structures, energetics, and reaction kinetics of atomic oxygen at SiO2/Si(100) interfaces are investigated based on
total-energy electronic-structure calculations within the density functional theory. It is found that oxygen atoms in the oxide
region form Si-O-O-Si bonds, whereas Si-O-Si bonds are formed in the substrate. It is also found that the reaction of atomic
oxygen is largely exothermic. A possible reaction mechanism for atomic oxygen is suggested from obtained structures.

Origin of Interfacial Reaction Constant for Si Thermal Oxidation, Toru AKIYAMA and Hiroyuki KAGESHIMA*: Extend
abstracts of the 2003 International Conference on Solid State Devices and Materials, Tokyo, pp. 490-491, 2003.
We present first-principles calculations that clarify mechanisms of reaction of oxygen molecules at SiO2/Si(100)interface. The energy barriers for the reaction of oxygen at the interface corresponds to the floating bond formation process
between the oxygen of oxidant and the host Si atom at the interface, and agree well with the experimentally reported activationenergies for ultrathin oxide. The present results imply that the accumulation of strain induced by oxidation crucially affect theinterfacial reaction. It is indicated that the origin of the activation energy of the reaction constant B/A in the Deal-Grove modeldue to this effect.

Microscopic Behavior of Atomic Oxygen at the SiO2/Si(100) Interface [in Japanese], Toru AKIYAMA and Hiroyuki
KAGESHIMA*: Extend abstracts of the 8-th Workshop on Formation, Characterization, and Reliability of Ultrathin Silicon
Oxides, pp. 273-277, 2003.
The atomic process of oxygen atom near the SiO2/Si(100) interface is studied based on total-energy electronic-structure
calculations. The calculations of O atoms in SiO2 indicate that O atoms diffuse by changing Si-O-O-Si bond (peroxy linkage
configuration) without forming isolated O atom configuration. It is found that calculated energy barriers for this mechanism arein the range of 0.6-1.0 eV. The energies of Si-O-Si bond at the top of Si substrate are much lower than those of O atom in SiO2.
The result indicates that the reaction in which an O atom in the oxide incorporated in the substrate is largely exothermic. It isalso found that the calculated energy barrier for this reaction is lower than the experimentally reported activation energy for theinterfacial reaction process in the dry oxidation. Detailed investigation for the atomic process of interfacial reaction is thus
important for the interpretation of experimentally reported activation energy.

Microscopic Mechanism of Interfacial Reaction during Si Oxidation, Toru AKIYAMA and Hiroyuki KAGESHIMA*:
Applied Surface Science 216, pp. 264-268, 2003.
The reaction of atomic oxygen at the SiO2/Si(100) interface is studied based on total-energy electronic-structure
calculations. It is found that the reaction in which an O atom in the oxide inserts into the Si-Si bond of the substrate is largely
exothermic. The calculated energy barrier of 0.87 eV for this reaction is lower than the experimentally reported activationenergy (2.0 eV) for the interfacial reaction in the dry oxidation. The results would help us clarify the microscopic mechanism of
Si oxidation, especially in identifying the form of oxidant in the dry oxidation.

Ａ−94

Abstracts of Papers

Dependence of the Magnetic Properties of TbFeCo Films on the Species of Sputtering Gases Used, Masahito MORIMOTO,
Tomohiro INAGAKI, Tadashi KOBAYASHI, Yuji FUJIWARA, Morio MASUDA, Shigeru SHIOMI and Tsutomu
SHIRATORI*: J. Magn. Soc. Jpn., 27, pp.269-272, 2003.
This paper investigates what the magnetic characteristics of TbFeCo films would become if Ar and Kr were used as
sputtering gases. The sample structure was glass / underlayer SiNx(u) / TbFeCo / protective layer SiNx(p), and the top threelayers were deposited by magnetron sputtering. When Kr gas was used, the coercive force Hc and effective perpendicularanisotropy Keff increased. The increase was not dependent on the difference in Curie temperature. The type of sputtering gas
used was changed for deposition of the SiNx(u) and TbFeCo layers. Consequently, Hc increased when TbFeCo was depositedby using Kr gas. Changing the kind of sputtering gas used seldom affected SiNx(u).

Magnetoresistance Effect of Co/AlO[x]/NiFe/Au/n-Si Diode Structure, Y. Fujiwara, T. Hirose, M. Jimbo, T. Kobayashi, M.
Masuda, Jpn. J. Appl. Phys. 42, pp L1009-L1011, 2003.
Magnetoelectronic properties were investigated for a Co/AlOx/NiFe/Au/n-Si diode structure utilizing thetwo-point-probe method at 77 K. In this system, electrons were transported from the Co layer to the n-Si substrate through the
AlOx tunneling barrier, NiFe magnetic layer and Au/n-Si Schottky barrier. When a positive bias (a reverse bias to Au/n-Si
Schottky diode) was applied between Co and n-Si, the current slightly increased with increasing positive bias voltage up to
approximately 0.75 V, and abruptly increased at a positive bias voltage over 0.75 V. The observed current showed a large
magnetoresistance effect of approximately 600%.

Material Processing Using Microorganisms (An Investigation of Microbial Action on Metals), Yasushi KUROSAKI, Masahito
MATSUI, Yuichi NAKAMURA, Kenichi MURAI and *Toshio KIMURA: JSME International Journal, Series C, Vol. 46, No.
1, pp. 322-330, 2003.
The possibilities for developing a new type of material processing using a microbiogenic function are investigated witha microbial corrosion test of metals under the sea water. The behavior of microorganisms in the corrosion of metals (mild steel,copper and aluminum sheets) is examined, and their action on these metals is discussed. As a result, three processing methods(biomachining, biodeposition and biorecycling) are proposed and discussed.

Oxygen Partial Pressure Dependences of a-c Phase Ratio, Crystallinity, Surface Roughness and In-Plane Orientation in YBCOThin Film Depositions by IBS, T. Endo, K Yoshii, S. Iwasaki, H. Kohmoto, H. Saratani, S. Shiomi, M. Matsui and Y. Kurosaki:
Proceedings of IUMRS International Conference on Electronic Materials (Xi'an 2002); Superconductor Science andTechnology, Vol. 16, pp.110-119, 2003.
YBa2Cu3OX thin films were grown on MgO by ion beam sputtering at various substrate temperatures TS and oxygen
partial pressures PO with a supply of either oxygen molecules or plasma (PL) to study fundamental crystal growth of perovskite
oxide. The a-phase growth is enhanced by PL due to two mechanisms, the collision retarded surface migration, and plasmaenergy assisted atomic rearrangement and surface energy reduction. The mixed film can release a strain energy from interiorgrain to ambient media, then it has good crystallinity but a rough surface. In contrast, the pure single a-phase film has poor
crystallinities but the smoothest surface because the strain energy is stored in the interior. In-plane orientation is improved byincreasing the a-phase ratio, and in-plane crystallinity can be improved by PL.

Abstracts of Papers
Ａ−95
Quantitative Estimation of Fracture Surface for Mild Steel Using Fractal Analysis, Mir Behdad KHAMESEE, Masahito
MATSUI, Kenichi MURAI, *Toshihide ISHIHARA and Yasushi KUROSAKI: Proceedings of the IMMM2003, pp.147-152,
2003.
The use of fractal dimension calculations, for quantitative classification of various objects, is well established in many
areas of the physical and life sciences. Such fractal dimension calculations are useful in that they furnish some measure ofgeometrical complexity that is not available through traditional approaches. In this research fractal analysis was applied forquantitative estimation of fracture surfaces. Fracture surface profiles of mild steel were generated under various kinds of notch
root (shape and radius) and tensile speed tests are examined by employing two methods of fractal analysis. A method forquantitative estimation of fracture surface phenomenon caused by fracture accidents is presented, and its validity is confirmed.
Although the fractography has used for texture determination of fracture surfaces, it is known that the surface fractography is
not enough for quantitative estimation of fracture surface but it is necessary. Even if under the same fracture type, fractal
dimension is not constant, but depends on the specimen shape, and thus on the fracture strain. By using fractal dimension andfractography as a method, fracture surface can be estimated.
Micro-Rheometry of Pressurized Lubricants and Micro-Nanorheology, Yuichi NAKAMURA and Yasushi KUROSAKI, Proc.
2003 JSME-IIP/ASME-ISPS Joint Conference on Micromechatronics for Information and Precision Equipment, pp.69-70,
2003.
In the present study, micro-rheometry of pressurized lubricants employing a diamond-anvil pressure cell and a laser
confocal displacement sensor of 0.4µm resolution was shown.. High pressure viscosity was obtained up to 2 GPa at 200 ℃
for traction oils and PFPE oils. The linearity between logarithmic viscosity and pressure is confirmed. Viscosity-pressure
coefficient α at room temperature was almost twice larger than that at 100 ℃. αfor hard disk oil, Zdol2000, was 13 /GPa at
24 ℃ 〜 5 /GPa at 150 ℃and was similar to that of paraffinic mineral oil. The feature of the obtained high pressure volume
was different for each oil up to 6 GPa. Zdol2000 was the most compressible of all the sample lubricants and its high pressurerefractive index increased about 10 % at 4.8 GPa. Zdol2000 remained transparent up to 4.8 GPa under isothermal loading.
Some considerations for lubricant's micro-nanorheology was also mentioned with high pressure lubricant's rheology.