MPI Kernphysik, Heidelberg Humboldt Univ. Berlin Ruhr-Univ. Bochum Univ. Hamburg
(Nagoya univ.) Yasuharu Kozuka, Asami Horiguchi, Hisanori Shiozawa, Ritsuko Tsuchiya, Hirofumi...
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Transcript of (Nagoya univ.) Yasuharu Kozuka, Asami Horiguchi, Hisanori Shiozawa, Ritsuko Tsuchiya, Hirofumi...
(Nagoya univ.) Yasuharu Kozuka, Asami Horiguchi, Hisanori Shiozawa, Ritsuko Tsuchiya, Hirofumi Yoshikawa, Kunio Awaga(Meijo univ.) Shunji Bandow, Sumio Ijima
Chemical Syntheses of Spherical Hollow Nanomagnets
Single Domain Magnet
· Down Sizing· Shape Control
Top-down
Bottom-up
N
S
N
S
~ 1 m
Bubble Domains in Co thin film
0 0 0 0 0 0 01 1 1 1
S
N
d (< 500 nm)
t (< 50 nm)
Domain Structure ?Thin film Effect ? Quantum Effect ?Catalysis ? Metal and Supercon. ?
Spherical Hollow Nanomagnet
Classification and physical phenomena of thin films
Thick film
Thin film
Thin film
Ultra Thin film Ultra high Thin film
100m
10m
m
m
100nm
10nm
1nm 0.1nm
100pm
~ 1000 atoms layer
~ 100 atoms layer
Particle size ofbulk magnetic material
vertical magnetization particle size, GMR
artificial latticewidth of quantum well
monoatomic layer(angstrom scale)
Elastic strain field of lattice defect, PMA
Macroscopicbulk
Mesoscopic
MicroscopicSuper lattice
Josephson deviceInsulation film
STM scale
Whisker non-transition crystal
HEMT activated layer
Thickness of magnetic wall
m 10–4
10–6
10–9
Å=10–10
diameter
thickness
Polystyrene Beads
Diameter = 100 ~ 1000 nm
Emulsion Polymerization
Water
HC CH2
n
Micelle
SEM
PS bead
Cu(NO3)2
(NH2)2CO( Thermal decomposition)
Aging at 85 ℃
Cu(CO3)2Cu(OH)2
500 ℃
Cu under H2
CuO in air500 nm
PS + Cu(NO3)2 + CO(NH2)2 + PVP [Cu(OH) 2 CuCO 3 ]85 ℃
( Poly Vinyl Pyrrolidone )
8
7
6
5
4
pH
6543210
Ti me (h)
N. Kawahashi, H. Shiho, J. Mater. Chem., 10, 2294 (2000).
Calcination
Homogeneous precipitation of metal hydroxides on PS beads
Concentrations of PS beads, Cu(NO3)2, CO(NH2)2, and PVP
Parameters are
Reaction temperature and time⑥
①
⑤
④③②
d = 460 nm 800 nm
SEM images of PS beads coated with Cu hydroxides
1 m 1 m
Size Effects
PS bead / nm Curie Const. / emu K g-1 Weiss const. / K
300 1.02 x 10-3 - 5.6
460 1.05 x 10-3 - 25
800 3.03 x 10-4 - 32
Surface area / g
m=0 paramagnet
m=7 weak ferromagnet
Cu Cu
O(H)
Cu2(OH)3(n-CmH2m+1COO)
Cu(NO3)2 Co(NO3)2
SEM image of PS beads (600 nm) coated with Co hydroxides
1 m
To get Co magnet
Flow meter
Furnace
Manostat
Vacuum pump
H2 bomb
Apparatus for Calcination
Sample
SEM
TEM
Calcination under H2 at 500 ℃ for 3 hrs PS beads d = 800 nm
850 nm
80 nm
fcc Co
X-ray powder diffraction pattern
T400 ℃
hcp fcc
RT Calcination
Co
Soft ferromagnet Coercive field < 40 Oe
Negligible temp. dependence
Magnetization curve at 2 K
Calcination
in Air
450 ℃6 hrs
500nm
Hollow spherical Co oxides
before after
2 K
Summary
Future works
• Syntheses of various metals and metal oxides hollow spheres
• Synthesis of cobalt hollow spheres in hcp phase
• Single particle magnetic measurements
• Hollow spherical nanomagnet of fcc-cobalt
• Soft magnet