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SYNTHETIC ENDEAVOURS TOWARDS
NEW SINGLE MOLECULE MAGNETS and
NEW SINGLE CHAIN MAGNETS
M. Verdaguer, Emeritus Professor Chimie
Inorganique et Matériaux Moléculaires, C.N.R.S.
Unit 7071 Université P. et M. Curie, Paris,
France miv_at_ccr.jussieu.fr
International Workshop on  Physics on Nanoscale
Magnets , Kyoto, 1-4 December 2003 NAREGI
Project, Kyoto Garden Palace Hotel
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SYNTHETIC ENDEAVOURS TOWARDS
NEW SINGLE MOLECULE MAGNETS and
NEW SINGLE CHAIN MAGNETS
Recents Results, Promises, Problems and Prospects
Coworkers and Collaborators V. Marvaud1, M.
Julve2, F. Villain1, W. Wernsdorfer3 F. Tuyèras1,
R. Lescouezec2, J.M. Herrera1, L.T. Marilena2, R.
Tiron3 N. Galvez1, R. Garde1, M. Hernandez1 1)
CIM2, CNRS Unit 7071, Université Pierre et Marie
Curie, Paris, France 2) Departament de Quimica
Inorganica, Universitat de Valencia, Burjassot,
Spain 3) Laboratoire Louis Néel, CNRS, Grenoble,
France
3
Outline
Introduction - molecular magnetism - the
molecular approach to nanosystems What a
chemist must can control ? From High Spin
Molecules to SSM - a systematic, rational,
approach - the photomagnetic way Single
Chain Magnets Conclusions
4
Chemistry
T, P, Solvent, pH
A B C
Reactants
Products
 Science of matters transformation
 A way to transform the world
5
M. Noyori, Hanoi, october 2003
To day the chemist is able to synthesize any
molecule at will
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A B C
Chemistry
How to choose A and B ?
or which target C ?
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Chemistry
which target C ?
-1- to make money (not always rewarding )
-2- to follow your supervisor (not always
recommendable )
-3- to answer questions of physicists ! or others
(sometimes amazing and useful)
-4- to achieve a synthetic challenge !
(difficult but worth of the candle)
-5- Many more
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One possible answer comes from
Molecular Magnetism
a scientific discipline that conceives designs
synthesizes studies and uses new molecular
magnetic materials
In a multidisciplinary way
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One of the nests of Molecular Magnetism
 Olivier Kahn was one of those who allowed to
switch from magnetochemistry to molecular
magnetism  D. Gatteschi, Lausanne, 2001
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Answering questions of physicists
the strange and successful story
of Haldane gap
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 Haldane gap
Conjecture (1983)
 Dynamic mass generation by the Néel magnon is
predicted  
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 Dynamic mass generation by the Néel magnon is
predicted  
Very clear and useful indication for synthesis
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 Haldane gap
Energy Gap in AF Integer spins 1D
 Translation 
Conjecture (1982)
Uniform Ni(II), S1 AF Chains
NENP TMNIN NINAZ many others
J.P. Renard et al., Europhys. Letters, 1987
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One of the central questions
Is it possible to use molecules (isolated metal
complexes) to build magnets ?
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Achieving a synthetic challenge
Overcome entropic and kinetics hindrances
A-L-B-L-A-L-Bn-
a ferrimagnetic bimetallic
molecule-based magnet at 4.6
K
M. Verdaguer et al., Coord. Chem. Reviews, 1998,
16
Synthetic challenge feasibility of a
bimetallic
molecule-based magnet ?
Bimetallic chains
AF Exchange Interaction between different spins
A. Gleizes et al. JACS 1981 et 1984, 3277 Y. Pei
et al. JACS 1986,
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Molecular Engineering vs Crystal Engineering
Bimetallic planes
AF between Chains After Displacement
NOW
Y. Pei et al., J. Am.Chem.Soc., 1988, 782
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Ferrimagnetic Bimetallic Chains
Molecular Engineering vs Crystal Engineering
Catena µ-Cu(II)(pba-OH)Mn(II)(H2O)2 Chain
Magnet at TC 4.6K
Hydrogen bonding
Interchain Interactions (af)
Y. Pei et al. J. Am. Chem. Soc. 1988, 110, 782
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Ferrimagnetic Bimetallic Chains
Molecular Engineering vs Crystal Engineering
Catena µ-Cu(II)(pba-OH)Mn(II)(H2O)2 Chain
Magnet at TC 4.6K
Hydrogen bonding
Interchain Interactions (af)
Y. Pei et al. J. Am. Chem. Soc. 1988, 110, 782
20
Achieving a synthetic challenge
a confidence problem
NB no long range order in 1D Let us go
to 3D
a brief story of a molecule-based magnet
at room temperature
M. Verdaguer et al., Coord. Chem. Reviews 1998,
190, 1023 Phil.Trans.A, 1999, 357, 2959.
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Synthetic challenge feasibility of a room
temperature
molecule-based magnet ?
Prussian Blue analogues
Exchange Interaction (1975, 1976)
V4Cr(CN)68/3n H2O and many others
TC 315K
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(No Transcript)
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from magnetochemistry to molecular magnetism
Blossoming of the discipline
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Switchable Systems Molecular Magnets Multifunction
al materials  Single Molecule  Magnets
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Single Molecule Magnet
Remains oriented after withdrawing of the field
(slow relaxation of the magnetisation )
WITHOUT Interaction between the molecules
Phenomenon strictly molecular !
WHY ?
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 Single molecule magnets
Giant Molecular Clusters
High Spin Anisotropy ?E DSz2
Mn12 Fe8
Mn4 and many others
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Top down
Fragments Threads Dots
New Physics Quantum / Classical Quantum
tunneling
Nice Chemistry Single molecule magnets
Giant Molecular Clusters
Applications (far ) Recording
Quantum computing
0D, Molecules
Bottom up
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Nanomagnets How ?Molecular Clusters

• No dispersion in size, in shape and in
  orientation
• Systems well characterised structure, magnetic
  parameters
• Control of parameters by synthesis

• Solubility
• Biocompatibility

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Single molecule magnets
without interaction between the molecules !
High Spin Anisotropic Molecules
Magnetisation reversal
DSz2
Anisotropy Barrier
and D lt 0
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Single molecule magnets
D 1K
(D lt 0)
DSz2 400K ?
S 20
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Remark if DGS gt 0
Within the ground state, Sz0 state is at
the lowest energy No more SMM
behaviour DGSlt0 is necessary for SMM
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Contro also transversal anisotropy E mixing of
M levels in Fe8 and central for Quantum tunneling
H DSz2 E(Sx2 -S2y) Terms(S4)
E/K
From D. Gatteschi, Florence
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Outline
Introduction molecular magnetism - the
molecular approach to nanosystems What a
chemist must can control ? From High Spin
Molecules to SSM - a systematic, rational,
approach - the photomagnetic way Single
Chain Magnets Conclusions
34
Outline
Introduction molecular magnetism - the
molecular approach to nanosystems What a
chemist must can control ? can ! From High
Spin Molecules to SSM - a systematic, rational,
approach - the photomagnetic way Single
Chain Magnets Conclusions
35
For the chemist Parameters to Control
S Spin D, E Anisotropy
J Exchange Constant Intramolecular
interaction zJ Intermolecular interaction
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Synthetic Strategy in Paris
Hexacyanometalate Heart Lewis Base
Mononuclear Complex Lewis Acid
Polynuclear Complex
Flexibility of the Synthetic Parameters
Metallic Cations, Polydendate ligands,
Counter-ions,
Solvents, Stoichiometry
Valérie Marvaud, A. Scuiller, F.Tuyèras, R.
Garde, (T. Mallah)
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Control of the ground spin state
Nuclearity
 Nature of the paramagnetic ions
 Exchange interaction J (F or AF) Symmetry
Control of the anisotropy
Molecular (and Crystal) Structure Symmetry
Electronic anisotropy (nature of the ions)
Control of the intermolecular interaction J 
Bulky ligands
Charged complexes and counterions
Dilution in an diamagnetic matrix
38
Outline
Introduction molecular magnetism - the
molecular approach to nanosystems What a
chemist must can control ? From High Spin
Molecules to SMM - a systematic, rational,
approach - the photomagnetic way Single
Chain Magnets Conclusions
39
Control of the ground spin state
Nuclearity
 Nature of the paramagnetic ions
 Exchange interaction J (F or AF) Symmetry
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Orbital Approach
Hexacyanochromate complex
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Magnetic Strategy 1) FERROMAGNETISM
M-C?N-M'
s
p
Cr(III)Ni(II)6 S 3/2 6x1 S 15/2
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Magnetic Strategy 2) FERRIMAGNETISM
M-C?N-M'
Overlap antiferromagnetism
Cr(III)Mn(II)6 S -3/2 6 x 5/2 S 27/2
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Heptanuclear Complexes
F
AF
F
Hexagonal R -3 a b 15,27
Å c 78,56 Å a b 90 g 120 V
4831 Å3
Hexagonal R -3 a b 15,27 Å
c 41,54 Å a b 90 g 120 V 8392 Å3
Hexagonal R -3 a b 23,32
Å c 40,51 Å a b 90 g 120 V
19020 Å3
Marvaud, Chemistry, 2003, 9, 1677 and 1692
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2nd generation
1rst generation
Complex
K. Vostrikova, P. Rey et al., JACS 2000, 122, 718
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S 14/2
Some examples
S 39/2 (AF), 51/2(F)
S 27/2
Rey, JACS 2000, 122, 718
Decurtins, Angewandte, 2000 Hashimoto, JACS, 2000
Marvaud, Chemistry, 2003, 9, 1677 y 1692
46
Fe2(Ni-R2)3
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Anisotropy A rational control is more difficult
! Two aspects - Structural - low symmetry
of the cluster - one anisotropy axis Cnv,
Dnh, - Electronic - local anisotropy of the
magnetic ions Di - exchange anisotropy Di,j
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Control of the anisotropy

• Isolated Ion Anisotropy Di
• Dipolar Interaction
• Anisotropic Exchange Di,j

D ?i ci Di ? ci,j D i,j
Can be computed (Genio Programme, D. Gatteschi)
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Marvaud et al., Chemistry, 2003, 9, 1677 and 1692
Ariane Scuiller, Caroline Decroix, Martine
Cantuel, Fabien Tuyèras
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CoCo2
CoNi2
CoCu2
7/2
CrNi2
5/2
CrNi
CoCu3
CoCo3 CrCo3
27/2
CrMn6
CoNi3 CrNi3
15/2
CoMn6
9/2
CrCu6
CrNi6
CoNi5 CrNi3
CoCo6
CoCu6
V. Marvaud
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 CrNi2  complexes molecules

CrIII, d3, t2g NiII , d8, eg Orthogonality
Ferro Spin 2x1 3/2 7/2 Structural anisotropy
CrIII(CN)4CN-NiII(tetren)2 Cl- or BF4-

S 7/2
Anisotropic molecular GdIII 
CrIII(CN)4CN-NiII(dienpy2)2 Cl-
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One of the most difficult problem
Control of INTERmolecular interactions J
i.e. crystal engineering
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 CrNi2  complexes cell packing
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Magnetism µ-SQUID Measurements
Magnetic Susceptibility
Easy axis F
Hard axis AF
Coll. W. Wernsdorfer, R. Tiron
See R. Tiron et al., Polyhedron, 2002,22, 2247
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Simplified scheme of unit cell
Cr(CN)4CN-Ni(tetren)2Cl
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Hysteresis loops vs temperature
H // easy axis
H // hard axis
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Hysteresis loops vs direction of H
H // easy axis
H // hard axis
Intermediate
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Hysteresis loops for 3 samples
H // hard axis
CrNi(tetren)2
CrNi(tetren)2
CrNi(dienpy2)2
59
Formally, the  same  molecules CrNi2
And slightly different properties
60
Two Isomeric Mn12
Mn12(p-MeBz)H2O
Mn12(p-MeBz)
D.N. Hendrickson, G. Christou et al.
61
Time necessary to relax 1 of MsatFe8D gt Fe8st gt
57Fe8
from D. Gatteschi, R. Sessoli et al.
62
Exchange-biased quantum tunnelling in a
supramolecular dimer of single-molecule magnets
S 9/2
J
S 9/2
W. Wernsdorfer, N. Aliaga-Alcalde, D. N.
Hendrickson G. Christou Nature 416, 406 (28
March 2002)
63
To get high spin and anisotropic
molecules some work in
progress
64
To get high spin and anisotropic molecules some
working directions
Well insulated
-V- Dilution in a dia/paramagnetic matrix
-VI- Interaction with light
V. Marvaud
65
Synthetic Strategy I
Cr(III)Ni(II)3, Tetranuclear Complex, C3v axis
Caracterisation
C3v
- Isostructural with CoNi3
- Mass Spectrometry M 1712.98

Magnetic Properties
Ferromagnetic Interaction
S 9/2
CrNi3, S9/2
J 9.70 cm-1, D -0.095 cm-1
Hexagonal R 3 a b 18,343 Å c 23,394
Å V 6818 Å3 , Z 3
Hysteresis at 30 mK
V. Marvaud, F. Tuyèras
66
Synthetic Strategy II
Using Anisotropic Ions, Co(II) and Mn(III) (large
D)
Magnetic Properties
Cristallographic Structure
Antiferromagnetic Interaction
S 5/2
J , D in progress
Cr(III)Mn(III)2
Monoclinic C 2/m a 17,821 Å b 14,275 Å
c 8,602 Å b 99,206
V. Marvaud, F. Tuyèras
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Synthetic Strategy III
Hetero tri metallic Complexes ,
Cr(III)Ni(II)2Mn(II)4
Synthesis
Cristallographic Structure

NiII
NiII
MnII
CrIII
S1
S3/2
S1
S 5/2
Trigonal R -3 a b 23,26 Å c
20,35 Å a b 90 g 120 V 9510 Å3
V. Marvaud, F. Tuyèras
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CrNi2Mn4 magnetic properties
Cr-Ni F Cr-Mn AF
Hexagonal R -3 a b 23,26 Å c 20,35
Å a b 90 g 120 V 9510 Å3
S (4 x 5/2) - 3/2 - (2 x 1) 13/2
Collaboration R. Sessoli D. Gatteschi
V. Marvaud, F. Tuyèras
69
CrNi2Mn4 High Field EPR
CrNi2
CrMn6
CrNi2Mn4
Coll.A.L. Barra D. Gatteschi
V. Marvaud, F. Tuyèras
70
CrNi2Mn4  Genio  Calculations
CrNi2Mn4 CNi 0,00833 CMn 0,11096 CCr
0,025
Looking for the best Hetero-Tri-Metallic Systems
CrNiL2 NiL4 predicted to be a  Single
Molecule Magnet 
Collaboration D. Gatteschi
V. Marvaud
71
Heterotrimetallic Complexes
CrNi2Mn4
CrNiMn5
CrNi4
And others !
V. Marvaud
72
Synthetic Strategy IV
Anisotropic Hearts
2 - Bidendates TRANS
3 - Trisdendates FAC y MER
4 - Tetradendates CIS
6 - Hexadendates
8 - Octadendates
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Polynuclear Complexes with Anisotropic Hearts
Fe(II)(phen)Cu(II)4
Fe(II)Cu(II)4
Monoclinic P 21/ a a 14,245 Å b 14,584
Å c 16,261 Å b 111,323
Monoclinic P 21/ n a 14,581 Å b 29,044
Å c 18,679 Å b 103,708
Fe(II), S 0 !
Ni(II) square planar, S 0 !
Fe(III) reduced to Fe(II)
74
Synthetic Strategy V
Dilution in a dia/paramagnetic matrix
CrNi2 diluted in a CoNi2 matrix
Cr(III) or Co(III)
NB Co(III), d6, diamagnetic
75
CrNi2 diluted in a CoNi2 matrix

• Quick Relaxation at H0
• Steeper magnetisation rise at lower T

Sigmoïdal signal is from matrix
Hope tunneling effect at H 0 SMM ?
76
Heptanuclear Complexes from octacyanometalate
precursors
WIVCuII6 MoIVCuII6
WIVNiII6 MoIVNiII6
WIVMnII6 MoIVMnII6
Monoclinic P n a 24.89 Å b 14,39 Å c
30,11 Å a g 90 b 108.81
Monoclinic C c a 25.39 Å b 15,22 Å c
30,72 Å a g 90 b 111.45
Monoclinic a 22.03 Å b 28,39 Å c 22,01
Å a g 90 b 99.48
V. Marvaud, J.M. Herrera, work in progress
77
Synthetic Strategy V
Interaction with light
Octacyanometalate Precursors Heptanuclear
Complexes
WIVCuII6 MoIVCuII6
WIVNiII6 MoIVNiII6
WIVMnII6 MoIVMnII6
Monoclinic P n a 24.89 Å b 14,39 Å c
30,11 Å a g 90 b 108.81
Monoclinic C c a 25.39 Å b 15,22 Å c
30,72 Å a g 90 b 111.45
Monoclinic a 22.03 Å b 28,39 Å c 22,01
Å a g 90 b 99.48
V. Marvaud, J.M. Herrera, work in progress
78
MoIVCuII6 photomagnetic molecule !
Magnetisation (H2T) at T 10K as f(irradiation
time)
M / u.a.
Time / min.
Collaboration C. Mathonière, ICMC Bordeaux
79
Photo-induced electron transfer
MoIVCuII6
MoVCuI1CuII5 MoV, d1 , S1/2 Ferro interaction
MoIV, d2 , S0 No exchange 6 isolated S1/2
S3
80
MoIVCuII6
?MT f(T) before irradiation and after
irradiation
? MT
hn
after
before
280 K
81
MoIVCuII6 further data
Magnetisation vs H at T 10K Experiment and
simulation
After irradiation -- Simulation (S3)
Before irradiation -- After cycling at
Room T
Fully reversible !
82
Outline
Introduction molecular magnetism - the
molecular approach to nanosystems What a
chemist must can control ? From High Spin
Molecules to SSM - a systematic, rational,
approach - the photomagnetic way Single
Chain Magnets Conclusions
83
Feasibility of  Molecular nanowires  ?
Anisotropic precursor
Fe(III)(bipy)(CN)4-
R. Lescouëzec, M. Julve, Valencia, Spain D.
Gatteschi, W. Wernsdorfer Angewandte Chem. 2003,
142, 1483-6
84
2 FeIII(bipy)(CN)4- CoII(H2O)62
Anisotropic precursor (Structure)
Anisotropic assembler (Electronic Structure)
FeIII, d5 bas spin S 1/2
CoII, d7 haut spin S 3/2
85
Bimetallic Chain ! FeIII(bipy)(CN)4
2CoII(H2O)24H2On
Cristallographic Structure (along a axis)
Monoclinic P21/n a 7,591Å b 15,190Å c
14,714Å ß 92,92
J. Vaissermann, Paris
86
Chain FeIII(bipy)(CN)4 2CoII(H2O)24H2On
Perspective View
7.59 Å (a)
J. Vaissermann
87
Chain catena-µ- FeIII(bipy)(CN)4
2CoII(H2O)24H2On
Few and Weak Interchains contacts
88
Chain catena µ- FeIII(bipy)(CN)4
2CoII(H2O)24H2On
View down axis a
Observe the angle between chains
89
Chain catena µ-FeIII(bipy)(CN)4
2CoII(H2O)24H2On
Magnetic Properties (powder)
FERROMAGNETIC INTERACTION !
90
Orbital interpretation Orthogonality of
Magnetic orbitals
R. Lescouëzec, J. Cano
91
Chain catena µ-FeIII(bipy)(CN)4
2CoII(H2O)24H2On
FCM plots along crystallographic axes a, b, c (H
5000 Oe)
92
Chain catena µ-FeIII(bipy)(CN)4
2CoII(H2O)24H2On
Magnetisation in the bc plane (H 5000 Oe T
5 K)
93
Chain catena µ-FeIII(bipy)(CN)4
2CoII(H2O)24H2On
Magnetisation in the bc plane (H 5000 Oe T
5 K)
94
Chain catena µ-FeIII(bipy)(CN)4
2CoII(H2O)24H2On
Single crystal ac susceptibility Measurements (SQ
UID)
Slow relaxation of the magnetisation !
? vs. T plots along the b axis.
R. Lescouezec, F. Lloret
95
Chain catena µ-FeIII(bipy)(CN)4
2CoII(H2O)24H2On
Magnetisation on microSQUID (microcrystal)
W. Wernsdorfer, LLN Grenoble
96
Chain catena µ-FeIII(bipy)(CN)4
2CoII(H2O)24H2On
MicroSQUID Single crystal measurements // b axis
Constant Temperature Varying Sweeping Rates
Slow relaxation of the magnetisation
W. Wernsdorfer, Grenoble
97
Chain catena µ-FeIII(bipy)(CN)4
2CoII(H2O)24H2On
MicroSQUID Single crystal measurements // b axis
Constant Sweeping Rate Varying Temperature
Slow relaxation of the magnetisation
W. Wernsdorfer, Grenoble
98
Slow relaxation of the magnetisation
Both ac and dc measurements indicate thermally
activated relaxation of the magnetisation ac
Ea 142 K, ?0 6.10-11 s dc Ea 43 K, ?0
2.10-8 s The different values of ?0 and Ea are
attributed to different relaxation processes.
M vs. t plots along the b axis.
W. Wernsdorfer, Grenoble
99
Slow relaxation of the magnetisation in 1D
1) New phenomenon See Gatteschi et al.
Angewandte Chemie, 2001 See Miyazaka, J. Am.
Chem. Soc. 2002 and this conference
2) Ising slow relaxing chains can be viewed as
1D nanomagnets or nanowires (or single chain
magnets)
3) Prospects - mechanisms of the magnetisation
reversal - local origin of the anisotropy
(CoII, FeIII, CoII-FeIII ?) - applications for
information storage ?
100
A flexible chemical system
Substitutions (pure or doped systems)  Co(II)
by Zn(II) (dia) Fe(III) by Co(III) (dia)
Co(II) / Zn(II)
Fe(III) / Co(III)
101
Slow relaxation of the magnetisation in 1D
4) Active field in progress - Search for
quantum tunneling in 1D
102
Is the regime becoming independent of
temperature ?
103
Outline
Introduction molecular magnetism - the
molecular approach to nanosystems What a
chemist must can control ? From High Spin
Molecules to SSM - a systematic, rational,
approach - the photomagnetic way Single
Chain Magnets Conclusions
104
Introduction What a chemist must can
control ? From High Spin Molecules to SSM - a
systematic, rational, approach - the
photomagnetic way Single Chain Magnets
Conclusions and acknowledgements
105
Everything possible in molecular magnetism ?
NO, but Molecular engineering Molecules in
the solid molecular engineering Subtleties
in structures and electronic properties But new
exciting fields - multifunctional
materials - molecular electronics quantum
computing
We did the easiest The most exciting is
coming, for young scientists
106
Prospects (short term)
New chemical systems with larger ?E
Improved Instrumentation (microSQUID  )
Prospects (long term)
Magnetic storage on ONE single molecule
 Quantum computing
107
Next  device   ? Recording on one molecule !
Exciting joint venture between physicists and
chemists theoreticians and experimentalists
108
6ème PCRD, NOE Proposal
Molecular Approach to Nanomagnets and
Multifunctional Materials
D. Gatteschi, Florence
109
Scientific exchanges
Hiroshima, November 23, 2002
Fuji-san, November 17, 2002
110
Acknowledgements
My coworkers
Research groups quoted
French Ministery of Higher Education
C.N.R.S
European TMR Molnanomag and M3D, ESF
Tokyo Institute of Technology
Professor Enoki Nagoya University
Professor
Awaga Organizers of the meeting
Professor Miyashita et alii
Kyoto November 14, 2002, Tofuku-ji garden
111
and YOU for kind attention
Kyoto November 2002 Imperial Palace Garden
112
Work partly done in Pierre Marie Curie
University
113
Acknowledgements
to my coworkers
Dante Gatteschi Chaire Blaise Pascal 2001
Valérie Marvaud
Anne Bleuzen
Christophe Cartier dit Moulin
Françoise Villain
Cyrille Train
R. Lescouëzec
Virginie Escax, Juan Manuel Herrera, Fabrice
Pointillart
A. Scuiller
Fabien Tuyèras, Guillaume Champion, Mannan
Seuleiman, Hayat Hanouti
S. Ferlay
Cédric Desplanches,Natividad Galvez, Ricardo
Moroni, Raquel Garde
V. Gadet