NMR-MRI, uSR and Mossbauer Spectroscopies in Molecular Magnets (eBook)

Preface 5
Contents 7
List of Contributors 9
Part I Nuclear Magnetic Resonance 11
A short introduction to Nuclear Magnetic Resonance 12
1 Precessing moments and the rotating frame 12
2 Time-evolution of nuclear magnetization and the Bloch equations 16
3 NMR spectra 18
4 Moment expansion of the NMR signal 19
5 Electron-nucleus hyperfine interaction 22
6 Effect of the motions on the NMR spectra 26
7 The spin echo 27
8 Nuclear spin-lattice relaxation rate 30
References 35
NMR in magnetic single molecule magnets 37
Contents 37
Introduction 37
1 General features of NMR in molecular nanomagnets. NMR spectra and hyperfine interactions 39
2 NMR and relaxation at high temperature (kT J). The spin dynamics in zero dimensions 47
3 NMR and relaxation at intermediate temperatures ( kT J). The spin dynamics in a collective total spin S quantum state 53
4 NMR at low temperatures ( kBT J). Nuclear spin lattice relaxation in gapped molecular antiferromagnets and effects at level crossing 59
5 NMR relaxation in single molecule magnets (SMM) in the ground state. Detection of quantum tunneling of the magnetization by NMR 65
Conclusions 74
References 75
Structure, synthesis and characterization of contrast agents for magnetic resonance molecular imaging 79
1 Introduction 79
2 Contrast agents 80
3 Relaxation mechanims 83
4 Physico-chemical characterization of contrast agents 86
5 Magnetic applications: MRI, cellular targeting 92
Conclusions 93
References 94
Basic concepts of Magnetic Resonance Imaging 96
1 Introduction 96
2 MRI physical principles and examples 96
3 Recent results on cerebral ischemia 111
a) b) 112
References 115
Phases, phase transitions and spin dynamics in strongly correlated electron systems, from antiferromagnets to HTC superconductors: NMR- NQR insights 118
1 Basic aspects of phase transitions and critical dynamics as reflected in NMR- NQR relaxation. 118
2 NMR-NQR insights on the phase transitions and spin dynamics in pure and in charge and spin- doped 2D S = 1/ 2 Heisenberg Antiferromagnets 133
3 Short-range correlation in AF spin-1 chains: insights 139
from 139
NMR in Y2BaNi1- 139
4 An overview on the main results from NMR-NQR studies in HTc superconductors, with emphasis on the vortex dynamics 142
5 Superconducting fluctuations: an overview of the studies based on the spin susceptibility ( Knight shift and T1) and on diamagnetic susceptibility 146
Part II Muon Spin Rotation 153
Introduction to µSR. 154
1 Introduction 154
2 The rules of the game 154
3 The muon fate at implantation 166
4 Paramagnetic chemical species 168
5 Magnetically ordered materials 171
6 Relaxation functions 175
References 181
Muon spin rotation of organic compounds 183
1 Introduction 183
2 Molecular magnetism 183
3 Muonium states 191
4 Conducting polymers 196
5 Molecular superconductors 199
6 Conclusion 208
References 209
Stochastic Landau-Zener model, and experimental estimates of dephasing time in molecular magnets. 213
1 Landau-Zener model in the presence of stochastic field fluctuations 214
2 Experimental dephasing time estimates 222
3 Conclusions 223
4 Acknowledgments 225
References 225
Part III Mössbauer Spectroscopy 226
Basic principles of M¨ ossbauer spectroscopy and applications 227
1 The Method 227
2 Novelty of gamma recoilless phenomena: the classic and the quantum approach 227
3 Lamb-M¨ ossbauer factor 228
4 M¨ ossbauer Parameters 230
5 M¨ ossbauer set-up 236
6 Presentation of selected experiments 241
7 Selected examples for the influence of external factors on M ¨ ossbauer spectra 242
Acknwoledgements 248
References 249
Line shape of M¨ ossbauer relaxation spectra 250
1 M¨ ossbauer cross section line shape 250
2 Time dependent hyperfine interactions and the relaxation superoperator 252
3 Evaluation of the relaxation superoperator matrix elements 255
4 Cross section evaluation 260
5 Result discussion 264
6 Saturation, texture and Goldanskii effects 268
Appendix: Liouville Operators 273
References 275
Studies of spin fluctuations in single molecular magnets by using M ¨ ossbauer spectroscopy 277
1 Molecules with S = 0 ground spin state 278
2 Molecules with S = 0 ground spin state 285
References 292