Magnetic nanoparticle assemblies

Magnetic nanoparticles with diameters in the range of a few nanometers are today at the cutting edge of modern technology and innovation because of their use in numerous applications ranging from engineering to biomedicine. A great deal of scientific interest has been focused on the functionalization of magnetic nanoparticle assemblies. The understanding of interparticle interactions is necessary to clarify the physics of these assemblies and their use in the development of high-performance magnetic materials.
This book reviews prominent research studies on the static and dynamic magnetic properties of nanoparticle assemblies, gathering together experimental and computational techniques in an effort to reveal their optimized magnetic properties for biomedical use and as ultra-high magnetic recording media.

Author Notes

Kalliopi N. Trohidou received her PhD from the University of Athens in 1988 with funding from the Greek Atomic Energy Agency, the British Council, and the Rutherford Appleton Laboratory. She worked in Great Britain as research fellow at the Rutherford Appleton Laboratory (19881989) and the University of Reading (19891990). From 1991 to 1993 she was research fellow at the Institute of Materials Science in NCSR Demokritos in Athens and then professor in the Department of Physics, Chemistry and Materials Technology at the Technical University of Piraeus (1993-1995). Her current research interests are theoretical studies and computational modeling of nanostructured materials. Dr. Trohidou has published more than 80 articles in scientific journals and several chapters in books. At present she is deputy director of the Institute of Advanced Materials, Physicochemical Processes, Nanotechnology and Microsystems and head of the Computational Materials Science group.

Georgia C. PapaefthymiouChris BinnsÒscar IglesiasMichael Fardis and Alexios P. Douvalis and George Diamantopoulos and Ioannis Rabias and Thomas Bakas and Hae Jin Kim and Georgios PapavassiliouDavide PeddisTh. Speliotis and D. NiarchosGang ChenMarianna Vasilakaki and George Margaris and Kalliopi N. Trohidou

Preface	p. xi
1 Biogenic and Biomimetic Magnetic Nanoparticles and Their Assemblies	p. 1
1.1 Introduction	p. 1
1.2 Biomineralization of Iron	p. 3
1.3 Bacterial Magnetomes	p. 4
1.3.1 Synthetic vs. Biogenic Nanomagnetite	p. 9
1.3.2 Microarraying of Magnetosomes	p. 12
1.4 Ferritin	p. 13
1.4.1 Nature of the Ferrihydrite Core	p. 15
1.4.2 Magnetic Properties of Ferritin	p. 18
1.5 Biomimetics	p. 23
1.5.1 Magnetoferritin	p. 25
1.5.2 Beyond Iron Oxides	p. 29
1.5.3 Metal and Metal Alloy Nanopartides	p. 31
1.6 Nanoparticle Superstructures	p. 34
1.6.1 Magnetoferritin Arrays	p. 35
1.6.1.1 3D arrays	p. 35
1.6.1.2 2D arrays	p. 39
1.7 Conclusion	p. 41
2 Controlling the Structure and Properties of Nanostructured Magnetic Materials Produced by Depositing Gas-Phase Nanopartides	p. 45
2.1 Introduction	p. 45
2.2 Pure Magnetic Nanoparticle Films	p. 47
2.2.1 Morphology of Pure Deposited Nanoparticle Films	p. 48
2.2.2 Magnetic Behavior of Pure Deposited Nanoparticle Films	p. 49
2.3 Magnetic Nanopartides in Matrices	p. 57
2.3.1 Controlling the Atomic Structure of Nanopartides in Matrices	p. 57
2.3.2 Controlling the Magnetic Properties of Isolated Nanoparticles in Matrices	p. 62
2.3.3 Controlling the Magnetic Properties by Nanoparticle Volume Fraction	p. 70
2.3.4 Producing Nanoparticle Hydrosols by Deposition of Gas-Phase Particles into Liquid Matrices	p. 81
3 Time-Dependent Phenomena in Nanoparticle Assemblies	p. 91
3.1 Magnetic Relaxation in Noninteracting Nanoparticle Ensembles	p. 95
3.2 Models of Interacting ID Chains of Nanoparticles	p. 100
3.3 Computational Details	p. 103
3.3.1 Calculation of Dipolar Energies	p. 103
3.3.2 The Monte Carlo Algorithm	p. 105
3.3.3 Dipolar Fields in ID	p. 106
3.4 Effective Energy Barrier Distributions	p. 107
3.5 Relaxation Curves: TIn[t/¿ 0 ) Scaling with Interactions	p. 109
3.5.1 Simulations of the Time Dependence of Magnetization	p. 110
3.5.2 T In(t/¿ 0 ) Scaling in the Presence of Interactions	p. 112
3.6 Evolution of f eff (E b ) and of Dipolar Fields	p. 114
3.7 Effective Energy Barrier Distributions from T In(t/¿ 0 ) Scaling	p. 117
3.8 Hysteresis Loops	p. 122
3.9 Conclusions	p. 124
4 Elementary Excitations in Magnetic Nanoparticles Probed with 57 Fe Nuclear Magnetic Resonance and Mossbauer Spectroscopy	p. 129
4.1 Introduction	p. 129
4.2 Magnetization Dynamics in Magnetic Nanoparticles	p. 132
4.2.1 Superparamagnetic and Blocking States	p. 132
4.2.2 Uniform Mode in Mossbauer and Nuclear Magnetic Resonance Spectroscopies	p. 135
4.2.2.1 Hyperfine magnetic field in Mossbauer spectroscopy	p. 135
4.2.2.2 Nuclear relaxation in nuclear magnetic resonance spectroscopy	p. 137
4.3 57 Fe Mössbauer Spectroscopy Experiments	p. 140
4.4 57 Fe Nuclear Magnetic Resonance Spectroscopy Experiments	p. 143
4.4.1 Nuclear Magnetic Resonance Line Shapes	p. 143
4.4.2 Nuclear T 2 Transverse Relaxation	p. 147
4.5 Concluding Remarks	p. 154
5 Magnetic Properties of Spinel Ferrite Nanoparticles: Influence of the Magnetic Structure	p. 159
5.1 Introduction	p. 159
5.2 Magnetism in Nanoparticles: An Introduction	p. 161
5.2.1 Magnetism in Condensed Matter	p. 161
5.2.2 Magnetic Single-Domain Particles	p. 163
5.2.3 Magnetic Anisotropy	p. 165
5.2.3.1 Magneto crystalline anisotropy	p. 166
5.2.3.2 Magnetostatic anisotropy (shape anisotropy)	p. 166
5.2.3.3 Surface anisotropy	p. 166
5.3 Magnetic Structure of Nanoparticles	p. 168
5.3.1 Spin Canting	p. 168
5.3.1.1 Temperature dependence of spin canting	p. 171
5.3.2 Iron Oxides with a Spinel Structure	p. 172
5.3.3 Spin Canting and Cationic Distribution: Magnetic Structure of Spinel Ferrite Nanoparticles	p. 174
5.4 Magnetic Properties of Spinel Ferrite Nanoparticles; Influence of the Magnetic Structure	p. 181
5.4.1 Surface Magnetism	p. 181
5.4.2 Magnetic Anisotropy	p. 186
5.4.2.1 Influence of the cationic distribution	p. 187
5.4.3 Saturation Magnetization	p. 188
6 FePt Films with Graded Anisotropy for Magnetic Recording	p. 199
6.1 Short History of Magnetic Recording	p. 199
6.2 Perpendicular Recording Media for 1 Tb/in 2 and beyond	p. 201
6.3 High Ku Materials	p. 204
6.4 Fabrication Methods	p. 207
6.4.1 Sputtering	p. 207
6.4.2 Thermal Evaporation	p. 208
6.4.3 Thin-Film Growth	p. 208
6.5 Technologies for Future Recording Media	p. 209
6.6 FePt Graded Media for Perpendicular Magnetic Recording	p. 211
6.7 Fundamental Properties of L1 0 FePt	p. 211
6.7.1 Optimization of FePt Single Layers onMgO	p. 211
6.7.2 L1 0 FePt on Amorphous Substrates	p. 214
6.7.2.1 Texture control and seed layer	p. 214
6.7.3 L1 0 FePt Based Exchange-Spring Phenomenon	p. 217
6.7.4 Production of Prototype L1 0 /A1 FePt Nanostructures	p. 217
6.7.4.1 L1 0 /A1 FePt semicore-shell nanocomposites	p. 218
6.7.5 Hard/Graded FePt Granular Layers	p. 219
6.7.5.1 Growth of L1 0 FePt/graded FePt nanocomposites prepared using UHV sputtering on MgO(002) substrates	p. 220
7 Fabrication of Patterned Nanoparticle Assemblies via Lithography	p. 227
7.1 Introduction	p. 227
7.2 Fabrication Techniques	p. 229
7.2.1 Direct Patterning Assembly	p. 229
7.2.2 Fabrication of NP Assemblies on Patterned Templates	p. 231
7.3 Summary and Perspective	p. 246
8 Magnetic Behavior of Composite Nanoparticle Assemblies	p. 253
8.1 Introduction	p. 253
8.2 The Model and Simulation Method	p. 260
8.2.1 Simulations of the Magnetic Behavior of Noninteracting Core/Shell Nanopartides in the Atomic Scale	p. 262
8.2.2 Simulations of the Magnetic Behavior of Interacting Core/Shell Nanopartides in the Mesoscopic Scale	p. 265
8.3 Magnetic Behavior of Noninteracting Core/Shell Nanoparticles: Study of Intraparticle Characteristics	p. 269
8.4 Magnetic Behavior of Interacting Core/Shell Nanopartides: Interparticle Interactions Effects	p. 273
8.4.1 Random Assemblies	p. 273
8.4.2 Ordered Arrays of Core/Shell Nanopartides	p. 278
8.5 Concluding Remarks	p. 280
Index	p. 287

Available:*

On Order

Summary

Summary

Author Notes

Table of Contents