1. (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

2. Single Domain Magnet · Down Sizing · Shape Control Top-down Bottom-up N S N S ~ 1  m

3. Bubble Domains in Co thin film 000000011 1 1 S N

4. d (< 500 nm) t (< 50 nm) Domain Structure ? Thin film Effect ? Quantum Effect ? Catalysis ? Metal and Supercon. ? Spherical Hollow Nanomagnet

5. Classification and physical phenomena of thin films Thick film Thin film Ultra Thin film Ultra high Thin film 100  m 10  m mm mm 100nm 10nm 1nm 0.1nm 100pm ～ 1000 atoms layer ～ 100 atoms layer Particle size of bulk magnetic material vertical magnetization particle size, GMR artificial lattice width of quantum well monoatomic layer (angstrom scale) Elastic strain field of lattice defect, PMA Macroscopic bulk Mesoscopic Microscopic Super lattice Josephson device Insulation 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

6. Polystyrene Beads Diameter = 100 ~ 1000 nm Emulsion Polymerization Water Micelle SEM

7. PS bead Cu(NO 3 ) 2 (NH 2 ) 2 CO （ Thermal decomposition ） Aging at 85 ℃ Cu(CO 3 ) 2 Cu(OH) 2 500 ℃ Cu under H 2 CuO in air 500 nm PS + Cu(NO 3 ) 2 ＋ CO(NH 2 ) 2 ＋ PVP [Cu(OH) ２ CuCO ３ ] 85 ℃ （ Poly Vinyl Pyrrolidone ） N. Kawahashi, H. Shiho, J. Mater. Chem., 10, 2294 (2000). Calcination Homogeneous precipitation of metal hydroxides on PS beads

8. Concentrations of PS beads, Cu(NO 3 ) 2, CO(NH 2 ) 2, and PVP Parameters are Reaction temperature and time ⑥ ① ⑤ ④③②

9. d = 460 nm 800 nm SEM images of PS beads coated with Cu hydroxides 1  m

10. Size Effects PS bead / nmCurie Const. / emu K g -1 Weiss const. / K 3001.02 x 10 -3 - 5.6 4601.05 x 10 -3 - 25 8003.03 x 10 -4 - 32 Surface area / g

11. m=0paramagnet m=7 weak ferromagnet Cu O(H)  Cu 2 (OH) 3 (n-C m H 2m+1 COO)

12. Cu(NO 3 ) 2 Co(NO 3 ) 2 SEM image of PS beads (600 nm) coated with Co hydroxides 1  m To get Co magnet

13. Flow meter Furnace Manostat Vacuum pump H 2 bomb Apparatus for Calcination Sample

14. SEM TEM Calcination under H 2 at 500 ℃ for 3 hrs PS beads d = 800 nm 850 nm 80 nm

15. fcc Co X-ray powder diffraction pattern T 400 ℃ hcpfcc RT Calcination Co

16. Soft ferromagnet Coercive field < 40 Oe Negligible temp. dependence Magnetization curve at 2 K

17. Calcinatio n in Air 450 ℃ 6 hrs 500nm Hollow spherical Co oxides beforeafter 2 K

18. 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