Takafumi MIYANAGA
Department of Advanced Physics, Professor
1960 born
1983 Kanazawa University (B.Tech)
1985 Kanazawa University (Ms.Tech)
1988 Osaka University (Dr.Sc)
1988 Hirosaki University (Assistant professor, Department of Physics)
1990-91 Simon Fraser University, visiting professor (Department of Physics)
1997 Hirosaki University (Associate Professor, Department of Materials Science
and Technology)
2003 Hirosaki University (Professor, Department of Materials Science and
Technology)
2006 Hirosaki University (Professor, Department of Advanced Physics)
Room:0702
Phone:0172-39-3551
FAX:0172-39-3551
e-mail: takaf@cc.hirosaki-u.ac.jp
Se non e vero, e
bene trovato
Research Interests:
· Condensed Matter Physics / Materials Science
· Structural Dynamics (Phase Transitions, Chemical Reactions, Surface Processes, Nonequilibrium states) , XAFS / Synchrotron Radiation
XAFS (X-ray Absorption Fine Structure) studies on
structurally disordered materials:
XAFS is a new method for structural analyses by using the synchrotron radiation
source. This is a special technique for the local structure because of the
short mean free path of the photoelectron. XAFS is applied to disordered
systems (glass transition and semiconductor to metal transitions in amorphous
and liquid As-Te and Se-Te systems) .
Quantum
Statistical Calculations for Debye-Waller Factor in XAFS, EELS and ARXPS
(Photoelectron Diffraction):
Thermal factors or Debye-Waller factors in the X-ray spectroscopy are
calculated from the framework of field theoretical method and path integral
approaches.
Structure and Dynamics of hevey fermion superconductors:
Cumulant analyses reveal the dynamics of the atom located in the double-well
potential. Lattling mechanism is important for the origin of the
superconducting phenomenon in PrOs4Sb12. EXAFS can investigate directly such a dynamics of
Lattling atoms.
Magnetic
XAFS (X-ray Magnetic Circular Dichroism):
Using circular polarized X-ray from the synchrotron radiation, we can detect
the local magnetic structures in the magnetic materials. XMCD is powerful for
disordered alloys, i.e. Ni-Mn alloys, in which atomic local order is important
for magnetic structure, and nano structural magnetic thin films.
Nanometer-Scale
Science and Technology:
XAFS studies on Thin Films and Mesoscopic Systems: Local structure of the
active thin layers in green and blue LED (InGaN single and
multiple-quantum-wells) by fluorescence XAFS using multi-element SSD. Ag
thin film and fine particles deposited on Si single crystal studied by total
conversion electron XAFS. The formation process of the Ag nano-clusters
in the cavity of the zeolites is studied by in-situ XAFS meaurements.
Core/Shell nano particle and its structre studied by XAFS.
Structural
Phase Transition in Perovskite Ferroelectric Materials:
Some Perovskites materials show the ferroelectricity and undergo the structural
phase transitions. XAFS reveals the mechanism of the structural phase
transition from the local point of view, which is complementary information
from difraction techniques by X-ray and neutrons. Landau theory of phase
transition.
Chemical
Physics/Soft Matters:
Quantum effect in the chemical reaction rate is calculated from the path-integral
approach. The relation between the ligand exchange reaction rate constant
and XAFS thermal factor can be analyzed from the view point of anharmonic
potential. Pattern formation in the complex systems; The formation
process of Konfeitos and snow road in winter.
XAFS for
Coordination Chemistry/Environmental:
Various 3d metal complexes, battery materials, the materials in environmentals
and Lanthnoid organometallic compounds were analyzed by using XAFS.
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Guide
line for graduate course lecture(pdf file)
Recent Publications:
l K.Nitta, Y.Omori, D.Kikuchi,
T.Miyanaga, K.Takegahara, H.Sugawara, H.Sato, Local Static Distortion of
Rare Earth Ions in ROs4Sb12 (R = La, Ce,
Pr, Nd, Sm) by Extended X-ray Absorption Fine Structure, 77, 063601-3 (2008).
l H.Ikemoto and T.Miyanaga, Extended X-ray
Absorption Fine Structure Study of Local Structure and Atomic Correlations of
Tellurium Nanoparticles, Phys. Rev. Lett, 99,
165503 (2007)
l T.Miyanaga, T.Azuhata, S.Matsuda,
Y.Ishikawa, S.Sasaki, T.Uruga, H.Tanida, S.F.Chichibu, T.Sota, Atomic
distribution in InxGa1-xN single-quanum-wells studied by
extended X-ray absorption fine structure, Phys. Rev. B, 76, 035314-1-5
(2007) .
l T.Miyanaga, T.Ogasawara, T.Okazaki,
Y.Sakisaka, K.Okamoto, S.Nagamatsu, T.Fujikawa, Local magnetic structures of
Ni-Mn alloys in ordered and disordered states studied by magnetic XAFS, J. Mag.
Mag. Mater., 310, e601-e603 (2007).
l T.Miyanaga, Y.Suzuki, S.Ohwada, M.Yamamoto,
T.Nanke, T.Kobayashi, A.Iwasaki, Local Structure of Ag/Au Core/Shell
Nano-Particles Studied by XAFS, e-J. Surf. Sci. Nanotech. 4, 138-143
(2006).
l K.Szymanski, D.Satula, L.Dobrzynski,
E.Volonina, E.P.Yelsukov, T.Miyanaga, Arrangements of magnetic moments in
nanocrystalline Fe48Al52. Phys. Rev. B 72, 104409 (2005)
l T.Miyanaga, T.Okazaki, R.Maruko,
S.Nagamatsu, T.Fujikawa, Y.Sakisaka, Mn K-edge magnetic EXAFS for Ni-Mn alloys,
Physica Scripta,T115, 632-634 (2005).
A more complete list of publications is availabvle here