1. Magnetization processes in V15
Awaji : 1 Dec. 2002
Magnetization processes in V15
Univ. Tokyo
S. Miyashita and K. Saito

2. Quantum Dynamics in Nanoscale Molecular Magnets
Resonant Tunneling Phenomena
Quantum Dynamics in Discrete Energy Levels
L. Thomas, et al. Nature
383 (1996) 167.
C. Sangregorio, et al.
PRL 78 (1997) 4645
I. Chiorescu, et al.
PRL 84 (2000) 3454.

3. Resonant Tunneling Discrete Energy level structure
J. M. Hernandez, et al.
PRB55(1997) 5858
Discrete Energy
level structure
J. A.A. J. Perenboom, PRB 58 (1998) 330

4. Nonadiabatic Transition
Quantum Dynamics in Discrete Energy Levels
Change in
Sweeping Field
Landau-Zener-Stueckelberg
Mechanism
C. Zener, Proc. R. Soc. (London)
Ser. A137 (1932) 696.
Resonant Tunneling
SM, JPSJ 64(1995) 3207, 65(1996) 2734.
H. De Raedt et al, PRB56 (1997) 2734

5. Quantum Dynamics Nonadiabatic Transition: Phase interference LZS, RZ
Nontrivial Resonance
SM, JPSJ 64 (1995) 3207,
H.De Raedt, SM, K. Saito, D. Garcia-Pablos
and N. Garcia, PRB 56 (1997)
SM, K. Saito and H. De Raedt,
PRL 80 (1998) 1525

6. Successive LZS transitions
Magnetization changes only when
H(t) crosses 0
SM & K. Saito, JPSJ (2001) 3238

7. Dissipation Effect Thernal Bath：Quantum Master equation
Random Noise： Quantum Schroedinger equation

8. Adiabatic transition and Relaxation
+ Thermal Bath
Pure Quantum
K. Saito, SM, H.de Raedt,
Phys. Rev. B60 (1999) 14553

9. V15 Adiabatic transition Phonon Bottleneck phenomena
I. Chiorescu, et al.
PRL 84 (2000) 3454.
Adiabatic transition
Effective S=3/2 system
I. Chiorescu, W. Wernsdorfer, A. Mueller, H. Boegge, B. Barbara,
Phys. Rev. Lett. 84 (2000) 3454.
K. Saito & SM. JPSJ (2001) 3385.
H. Nakano & SM, JPSJ 70(2001) 2151

10. Tunneling in half-odd integer spin systems
Tunneling Probability
Half-interger、Time　Reversal　Sym.
Kramers doublet
Single spin mode
Multi-spin model + DM
Two avoided cross structures
Adiabatic change of M(H)
SM, &. N. Nagaosa,
Prog. Theor. Phys. 106 (2001) 533

11. ５spin-model
I. Rudra, S. Ramasesha, and D. Sen, J. Phys. Cond. Mat. 13 (2001) 11717
N. P. Konstantinidis and D. Coffey, cond-mat
I. Rudra, K. Saito, S. Ramasesha and S. Miyashita, preprint

12. Effective interaction
SM, &. N. Nagaosa,
Prog. Theor. Phys. 106 (2001) 533

13. Energy structure Quasi-degenerate avoided level crossing structures
4 states
LZS formula
works well

14. 4-dimensional irreducible space
Overlap of the wave function

15. Nonadiabatic Transition in the Field Sweeping
Transition probability of Magnetization

16. Adiabatic process in V15 Phonon Bottleneck phenomena
Plateau induced by thermal effect
Chiorescu, W. Wernsdorfer,
A. Mueller, H. Boegge, B. Barbara,
Phys. Rev. Lett. 84 (2000) 3454.

17. Reduced Density Matrix
Boson Bath
K. Saito, S. Takesue and SM. Phys. Rev. B61 (2000) 2397

18. Field sweeping with thermal bath
Fast sweeping
Slow sweeping
Magnetic
FoehnEffect
LZS
K. Saito & SM.
JPSJ (2001) 3385.

19. Nonadiabatic Tr. & Heat-inflow
LZ transition
Magnetic Foehn Effcet

20. Non-monotonic M(H)

21. Fe2 Fe-rings Y. Shapira, et al PRB59 (1999) 1046 Y. Ajiro & Y. Inagaki
Y. Narumi & K. Kindo
H. Nakano & SM, JPSJ 70(2001) 2151

22. Time scales in the simulation

23. V15

24. Diagonalization of L

25. V15-MFE

26. V15-magnetization relaxation
I. Chiorescu, W. Wernsdorfer, A. Mueller, S. Miyashita
and B. Barbara, preprint

27. Relation to the longitudinal relaxation
slow sweeping
fast sweeping
magnetic Feohn
isothermal
adiabatic

28. Effects of doubly degenerate structure
Transition from 1/ /2

29. Transition from 1/2 to 3/2 Symmetry change from A to E Matrix elements
for ESR

30. Hidden Conservation Law?
Equilibrium
process
Adiabatic change
SM, &. N. Nagaosa, Prog. Theor. Phys. 106 (2001) 533

31. Hysteresis in field sweep

32. Resonance on the AC field Non-trivial Resonance
F. Grossman,et al. PRL 67 (1991) 516.
Y. Kayamuma, PRB 47 (1993) 9940
S.Miyashita, K. Saito, H. De Daedt, PRL 80 (1998) 1525.

33. AC field and `effective ’ gap

34. Floquet eigenvalue

35. Omega=0.1

36. Omega=0.001
<M(t)>
0.02 t

37. Quantum Phase Effect Berry phase Control of Energy Gap by
The External Field
W.Wernsdorfer & R. Sessoli: Science 284 (1999) 133

38. c.f. Spin-rotation pulse
Transverse oscillating filed

39. Effective gap due to the AC field
Reduce the too large gap to observe the
quantum oscillation of the magnetization in time
AC field effect on the sweeping
Y. Kayanuma and Y. Mizumoto:
PRA 62 (2000)

40. Sweep with AC field

41. Sweep with AC field2
<M(t)> t

42. Sweep with AC field 3
avalanche ?

43. Hz resonance

44. Classical Switching and Quantum Switching
Switching：　2-values＋Metastability
Classical：　Dissipation
Ferromagnetic order＋
Hysteresis　
Quantum : Dynamics
Quantum States+
Adiabatic change

45. Thank you for your attention
Look for some intrinsic effects
due to
the real time quantum dynamics
Thank you for your attention

46. Local magnets due to inhomogeneity
Heisenberg AF chain: Haldane state
F. D. M. Haldane,Phys. Lett. 93A (1983) 464.
Phys. Rev. Lett. 50(1983) 1153
Edge States
Impurity Effects
P. Roos and SM,
PRB59 (1999) 13782
SM, S. Yamamoto, Phys. Rev. B48(1993) 915

47. Inhomogeneity induced magnetization
M. Nishino, H. Onishi, K. Yamaguchi & SM: PRB62 (2000) 9463

48. Quantum Langevin Equation
Non-white random field
Noise Amplitude >> Gap

49. Square-root time dependence
Resonat Tunneling
Relaxation
C. Sangregorio, T. Ohm, C. Paulsen, R. Sessoli & D. Gatteschi, PRL 78 (1997) 4645.
L. Thomas et al. PRL 83 (1999) 2398.
Hole digging phenomena
Square-root time
Initial decay of M(t)
W. Wernsdorfer, et al.
PRL 82 (1999) 3903

50. Phenomenological theory

51. SQ-phenomeno