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MAGNETISM
Materials and Applications
Front Cover Photo:Courtesy of Pierre Molho, Laboratoire Louis Néel du CNRS, Grenoble, France.A computer hard disk drive, a device combining many state-of-the-art magnetictechnologies (courtesy of Seagate Corporation). The unit is set against a magneticdomain pattern in a garnet film, imaged through the mageneto-optical Faraday effect;the domain width is about 7 um (courtesy Pierre Molho, LaboratoireLouis Néel du CNRS, Grenoble, France).
MAGNETISM
Materials and Applications
Edited by
Étienne du TRÉMOLET de LACHEISSERIEDamien GIGNOUX
Michel SCHLENKER
Springer
eBook ISBN: 0-387-23063-7Print ISBN: 0-387-23000-9
Print ©2005 Springer Science + Business Media, Inc.
All rights reserved
No part of this eBook may be reproduced or transmitted in any form or by any means, electronic,
mechanical, recording, or otherwise, without written consent from the Publisher
Created in the United States of America
Boston
©2005 Springer Science + Business Media, Inc.
Visit Springer's eBookstore at: http://ebooks.kluweronline.comand the Springer Global Website Online at: http://www.springeronline.com
AUTHORS
Michel CYROT - Professor at the Joseph Fourier University of Grenoble, France
Michel DÉCORPS - Senior Researcher, INSERM (French Institute of Health andMedical Research), Bioclinical Magnetic Nuclear Resonance Unit, Grenoble
Bernard DIÉNY - Researcher and group leader at the CEA (French Atomic EnergyCenter), Grenoble
Etienne du TRÉMOLET de LACHEISSERIE - Senior Researcher, CNRS,Laboratoire Louis Néel, Grenoble
Olivier GEOFFROY - Assistant Professor at the Joseph Fourier University ofGrenoble
Damien GlGNOUX - Professor at the Joseph Fourier University of Grenoble
Ian HEDLEY - Researcher at the University of Geneva, Switzerland
Claudine LACROIX - Senior Researcher, CNRS, Laboratoire Louis Néel, Grenoble
Jean LAFOREST - Research Engineer, CNRS, Laboratoire Louis Néel, Grenoble
Philippe LETHUILLIER - Engineer at the Joseph Fourier University of Grenoble
Pierre MOLHO - Researcher, CNRS, Laboratoire Louis Néel, Grenoble
Jean-Claude PEUZIN - Senior Researcher, CNRS, Laboratoire Louis Néel, Grenoble
Jacques PIERRE - Senior Researcher, CNRS, Laboratoire Louis Néel, Grenoble
Jean-Louis PORTESEIL - Professor at the Joseph Fourier University of Grenoble
Pierre ROCHETTE - Professor at the University of Aix-Marseille 3, France
Michel-François ROSSIGNOL - Professor at the Institut National Polytechnique deGrenoble (Technical University)
Yves SAMSON - Researcher and group leader at the CEA (French Atomic EnergyCenter) in Grenoble
Michel SCHLENKER - Professor at the Institut National Polytechnique de Grenoble(Technical University)
Christoph SEGEBARTH - Senior Researcher, INSERM (French Institute of Healthand Medical Research), Bioclinical Magnetic Nuclear Resonance Unit, Grenoble
Yves SOUCHE - Research Engineer, CNRS, Laboratoire Louis Néel, Grenoble
Jean-Paul YONNET - Senior Researcher, CNRS, Electrical Engineering Laboratory,Institut National Polytechnique de Grenoble (Technical University)
Grenoble Sciences
“Grenoble Sciences” was created ten years ago by the Joseph Fourier University ofGrenoble, France (Science, Technology and Medicine) to select and publish originalprojects. Anonymous referees choose the best projects and then a Reading Committeeinteracts with the authors as long as necessary to improve the quality of themanuscript.
(Contact : Tél.: (33)4 76 51 46 95 - E-mail : [email protected])
The “Magnetism” Reading Committee included the following members :
V. Archambault, Engineer - Rhodia-Recherche, Aubervilliers, FranceE. Burzo, Professor at the University of Cluj, RumaniaI. Campbell, Senoir Researcher - CNRS, Orsay, FranceF. Claeyssen, Engineer - CEDRAT, Grenoble, FranceG. Couderchon, Engineer - Imphy Ugine Précision, Imphy, FranceJ.M.D. Coey, Professor - Trinity College, Dublin, IrelandA. Fert, Professor - INSA, Toulouse, FranceD. Givord, Senior Researcher - Laboratoire Louis Néel, Grenoble, FranceL. Néel, Professor, Nobel Laureate in Physics, Member of the French Academy ofScienceB. Raquet, Assistant Professor - INSA, Toulouse, FranceA. Rudi, Engineer - ECIA, Audincourt, FrancePh. Tenaud, Engineer - UGIMAG, St-Pierre d’Allevard, France
“Magnetism” (2 volumes) is an improved version of the French book published by“Grenoble Sciences” in partnership with EDP Sciences with support from the FrenchMinistry of Higher Education and Research and the “Région Rhône-Alpes”.
VI
BRIEF CONTENTS
I - FUNDAMENTALS
Foreword
Phenomenological approach to magnetismMagnetism, from the dawn of civilization to today - E. du Trémolet de Lacheisserie
Magnetostatics - D. Gignoux, J.C. Peuzin
Phenomenology of magnetism at the macroscopic scale - D. Gignoux
Phenomenology of magnetism at the microscopic scale - D. Gignoux
Ferromagnetism of an ideal system - M. Rossignol, M. Schlenker, Y. Samson
Irreversibility of magnetization processes, and hysteresis in real ferromagnetic materials:
the role of defects - M. Rossignol
1
2
3
4
5
6
Theoretical approach to magnetismMagnetism in the localised electron model - D. Gignoux
Magnetism in the itinerant electron model - M. Cyrot
Exchange interactions - C. Lacroix, M. Cyrot
Thermodynamic aspects of magnetism - M. Schlenker, E. du T. de Lacheisserie
7
8
9
10
Coupling phenomenaMagnetocaloric coupling and related effects - E. du Trémolet de Lacheisserie, M. Schlenker
Magnetoelastic effects - E. du Trémolet de Lacheisserie
Magneto-optical effects - M. Schlenker, Y. Souche
Magnetic resistivity, magnetoresistance, and the Hall effect - J. Pierre
11
12
13
14
AppendicesSymbols used in the text
Units and universal constants
Periodic table of the elements
Magnetic susceptibilities
Ferromagnetic materials
Special functions
Maxwell’s equations
1
2
3
4
5
6
7
General references
Index by material and by subject
II - MATERIALS AND APPLICATIONS
Foreword
Magnetic materials and their applicationsPermanent magnets - M. Rossignol, J.P. Yonnet
Soft materials for electrical engineering and low frequency electronics - O. Geoffroy, J.L. Porteseil
Soft materials for high frequency electronics - J.C. Peuzin
Magnetostrictive materials - E. du Trémolet de Lacheisserie
Superconductivity - M. Cyrot
Magnetic thin films and multilayers - B. Dieny
Principles of magnetic recording - J.C. Peuzin
Ferrofluids - P. Molho
15
16
17
18
19
20
21
22
Other aspects of magnetismMagnetic resonance imaging - M. Décorps, C. Segebarth
Magnetism of earth materials and geomagnetism - P. Rochette, I. Hedley
Magnetism and the Life Sciences - E. du Trémolet de Lacheisserie, P. Rochette
Practical magnetism and instrumentation - Ph. Lethuillier
23
24
25
26
AppendicesSymbols used in the text
Units and universal constants
Periodic table of the elements
Magnetic susceptibilities
Ferromagnetic materials
Economic aspects of magnetic materials - J. Laforest
1
2
3
4
5
6
General references
Index by material and by subject
VIII
TABLE OF CONTENTSII - MATERIALS AND APPLICATIONS
Foreword by Professor Louis Néel
Preface
Acknowledgements
XXI
XXIII
XXIV
MAGNETIC MATERIALS AND THEIR APPLICATIONS
15 - Permanent magnets1. Implementation of magnets
1.1. The two hysteresis loops of a material: magnetization loop M(H)and induction loop B(H)
1.2. Operation of an ideal permanent magnet within a systemLoad line and working point of a magnetStatic and dynamic operation of a permanent magnetThe maximum energy product (static operation)Free energy involved in the dynamic operation of a magnet
Performance parameters of real magnet materialsMagnetization and induction loops of various hard magnetic materialsThe maximum energy productPerformance parameters, and their range of variation
Oriented (textured) and isotropic magnetsMagnet classificationComparison of the magnetic behavior of oriented and isotropic magnets
Principal industrial magnet materialsThe various types of sintered and oriented magnets
AlNiCo magnetsFerrite magnetsSamarium-cobalt magnetsNeodymium-iron-boron magnets
Parameters and typical curvesSintered and oriented magnetsBonded magnets
Uses of permanent magnetsThe principal fields of permanent magnet applications
MiniaturizationPermanent field sourcesRepelling magnets
Properties of industrial magnetsPrincipal properties of the AlNiCo magnetsMain characteristics of ferrite magnetsMain properties of rare earth magnets
1.2.1.1.2.2.1.2.3.1.2.4.
1.3.1.3.1.1.3.2.1.3.3.
2.2.1.2.2.
3.3.1.
3.1.1.3.1.2.3.1.3.3.1.4.
3.2.3.2.1.3.2.2.
4.4.1.
4.1.14.1.2.4.1.3
4.2.4.2.1.4.2.2.4.2.3.
3
4
44578
1010101112
141415
171718181819191920
212121232324242526
Electromagnetic systemsThe evolution of motorsPermanent magnet actuators
Magnetomechanical systemsMagnetic bearingsMagnetic couplings
Field sourcesSensorsEddy current systemsField source
Modelling permanent magnet systemsClosed circuit calculationsOpen circuit calculationsNumerical methodsMagnet characteristics
Magnet materials: microstructure and preparation techniquesCoercivity and how to enhance it
Strong uniaxial anisotropyThe role of defects and the need for a microstructure
The magnet material must be reduced to fine particlesReduction into grains to suppress nucleationReduction into grains to increase remanence and the squareness of the M(H) loop
General principles of the processes used to prepare magnet microstructuresOriented sintered magnetsCoercive powders and bonded magnets
The basic materials for permanent magnetsMagnetic characteristics of 3d and 4f elementsvs the properties required to obtain a hard magnetic material
Magnetic moments and exchange interactions in rare earth and transition metalsMagnetocrystalline anisotropy of 3d and 4f elements
Transition metal based magnet materialsR-M intermetallic alloys (R = rare earth, M = transition metal)
R-M exchange coupling, via the d electronsR-M coupling = ferromagnetism or ferrimagnetismMagnetocrystalline anisotropy in R-M compoundswith uniaxial crystallographic structure: easy axis or easy plane
Review of intermetallic compoundsBinary compoundsTernary compoundsInterstitial ternary compounds
Magnetization reversal mechanismsMagnetization reversal in magnetic systems devoidof magnetocrystalline anisotropy: application to AlNiCo magnetsMagnetization reversal in systems with strong magnetocrystalline anisotropy:non-collective reversal in stages
Stages of the processThe driving forces of reversal: magnetic fields and thermal effects
The magnetization reversal fieldrelationship with the intrinsic magnetic properties of the principal phase
as a function of and local dipolar effectsas a function of the energy barrier for the critical mechanism
4.3.4.3.1.4.3.2.
4.4.4.4.1.4.4.2.
4.5.4.5.1.4.5.2.4.5.3.
4.6.4.6.1.4.6.2.4.6.3.4.6.4.
5.5.1.
5.1.1.5.1.2.
5.2.5.2.1.5.2.2.
5.3.5.3.1.5.3.2.
6.6.1.
6.1.1.6.1.2.
6.2.6.3.
6.3.1.6.3.2.6.3.3.
6.4.6.4.1.6.4.2.6.4.3.
7.7.1.
7.2.
7.2.1.7.2.2.
7.3.
7.3.1.7.3.2.
272829303031323233343636363739
39394040404141424244
45
45464748515155
5657586263
64
64
666667
676869
X
Which mechanism determines magnetization reversal?Analysis of the initial magnetization curve, particularly the initial susceptibilityObservation of domains and domain wall motionin the thermally demagnetised stateVariation of the reversal field with the direction of the applied field:Modelling of the different mechanisms involvedin non-collective magnetization reversal
Exercises
Solution to the exercises
References
16 - Soft materials for electrical engineering and low frequency electronicsGeneral presentation of soft materials
The properties required of a soft materialRole of structural and electromagnetic characteristics
PolarizationPermeabilityEnergy dissipation
Energy loss analysisMacroscopic aspectsCalculation of losses in a conductor
Losses in rotating or trapezoidal field
Iron based crystalline materialsIron and soft steelsClassical iron-silicon alloysFe-Si sheets with non oriented (NO) grains
Magnetic characteristicsApplicationsEvolution and prospects of NO sheets
Grain-oriented (GO) Fe-Si sheetsDomain structure optimizationMagnetic characteristics
Thin iron-silicon sheetsHigh silicon content alloys
Alloys obtained by fast solidificationDiffusion enriched alloys
Iron-nickel and iron-cobalt alloysIron-nickel family
Alloys around 30% NiAlloys around 50% NiAlloys around 80% Ni (Permalloys)
Iron-cobalt alloys
Soft ferritesElectromagnetic properties
Saturation polarizationCurie temperatureAnisotropyMagnetostrictionResistivityPermeability - cutoff frequency product
7.4.7.4.1.7.4.2.
7.4.3.7.4.4.
1.1.1.1.2.
1.2.1.1.2.2.1.2.3.
1.3.1.3.1.1.3.2.
1.4.
2.2.1.2.2.2.3.
2.3.1.2.3.2.2.3.3.
2.4.2.4.1.2.4.2.
2.5.2.6.
2.6.1.2.6.2.
3.3.1.
3.1.1.3.1.2.3.1.3.
3.2.
4.4.1.
4.1 .1.4.1.2.4.1.3.4.1.4.4.1.5.4.1.6.
7171
7273
75
76
81
86
89
89909090919292929396
9696979999
100100101102103104105105107
108108109109110111
112112112112113113113113
XI
Applications of ferritesPower electronicsLow power applications
Amorphous alloysGeneral characteristicsMain classes of soft amorphous alloys
High polarization alloysLow magnetostriction alloys
Applications of amorphous alloys
Nanocrystalline materialsElectromagnetic characteristics
PolarizationAnisotropyMagnetostrictionResistivityUniaxial induced anisotropy
Random anisotropy modelApplications of nanocrystalline materials
Energy conversion at industrial frequencies (50-400 Hz)Distribution transformersRotating machines
A refresher on magnetic system energyApplication to the study of some structuresThe main classes of machinesSoft magnetic materials used in rotating machines
ActuatorsAn example of a rotating actuator: stepping machine with variable reluctanceChoice criteria, orders of magnitude
Energy transformation in power electronicsSmoothing inductances, and components for inductive energy storageRequirements associated with high frequencyControl-power interfacing
Maximum pulse lengthResponse timeComment on the static switch
Exercises: study of a voltage stabilizing device using a saturable inductance
Solutions to the exercices
References
17 - Soft materials for high frequency electronicsComplex susceptibility and permeability
Isotropic complex susceptiblity and permeabilityPhysical meaning of andGeneral dynamic regimeKramers-Kronig relations
Anisotropic materials. Complex susceptibility and permeability tensors
Measuring the complex susceptibility and permeabilityInternal and external susceptibilities
External susceptibility in a simple caseEffect of the demagnetising field on the drifts and lossesSkin effect and dimensional resonance
4.2.4.2.1.4.2.2.
5.5.1.5.2.
5.2.1.5.2.2.
5.3.
6.6.1.
6.1.1.6.1.2.6.1.3.6.1.4.6.1.5.
6.2.6.3.
7.7.1.7.2.
7.2.1.7.2.2.7.2.3.7.2.4.
8.8.1.8.2.
9.9.1.9.2.9.3.
9.3.1.9.3.2.9.3.3.
1.1.1.
1.1.1.1.1.2.1.1.3.
1.2.
2.2.1.
2.1.1.2.1.2.2.1.3.
114114114
114115115115116116
117118118118118119119119121
122123127127128132134
134135141
143143144146146146147
148
151
153
155
155156156157158158
159159160160161
XII
Reciprocity theoremMeasuring by perturbation of a coilTwo coil measurementFrequency limitations in coil methodsMeasuring toroidal samples
Elementary susceptibility mechanismsRotation mechanism
Isotropic rotation (or uniaxial symmetry)Anisotropic rotation
Wall mechanismBallistic behavior - Döring massIntroducing damping - Wall mobilityEquation of motion for an isolated plane wallGeneralization to curved wallsDiffusion relaxationDisaccommodation
Susceptibility in the demagnetised state: the homogenization problemThe approximation of additivity or of the mean
Snoek’s modelThe model of Globus et al.
Effective medium modelWall contribution and rotation contribution
Susceptibility in the saturated state - Magnetostatic modesCircular susceptibilities and permeabilities - GyrotropyUniform magnetostatic resonanceNon uniform resonance: magnetostatic modesThe role of exchange interaction: spin waves
An overview of radio-frequency materials and applicationsSpinelsPlanar hexaferritesApplications in linear inductive components
Overview of microwave materials and applicationsThe ferrimagnetic garnetsMicrowave applications
Non-reciprocal devicesTunable resonatorMicrowave absorbers
Appendix: the effective medium method
Exercises
Solutions to the exercises
References
18 - Magnetostrictive materialsThe Invar and Elinvar family
Controlled thermal expansion alloysAlloys with constant elastic moduli
Magnetostrictive materials for actuatorsMaterials with high anisotropic magnetostrictionTerfenol-D
2.2.2.3.2.4.2.5.2.6.
3.3.1.
3.1.1.3.1.2.
3.2.3.2.1.3.2.2.3.2.3.3.2.4.3.2.5.3.2.6.
4.4.1.
4.1.1.4.1.2.
4.2.4.3.
5.5.1.5.2.5.3.5.4.
6.6.1.6.2.6.3.
7.7.1.7.2.
7.2.1.7.2.2.7.2.3.
1.1.1.1.2.
2.2.1.2.2.
162162163164164
166167168171173174176176177177178
178179179180181183
184184185187189
190191193194
197197198198202203
204
209
210
210
213
213213215
216216216
XIII
Use of Terfenol-D in actuatorsLinear actuatorDifferential actuatorWiedemann effect actuatorsMagnetostrictive linear motorMagnetostrictive rotary motorsSonar
Sensor materialsMetglas 2605SCSensors based on inverse magnetoelastic effects
Force sensorUltrasensitive magnetometryInverse Wiedemann effect torquemeter
Sensors based on direct magnetoelastic effectsMagnetostrictive magnetometersPosition detector
Integrated actuators and sensors
Conclusions and perspectives
Exercises
Solutions to the exercises
References
19 - SuperconductivityIntroduction
Definition of superconductivity
Some fundamental properties of superconductorsThermodynamic critical field and critical currentCharacteristic lengths
Physical effects related to the phaseFlux quantization in a ringJosephson effectAC Josephson effectDynamics of a shunted junction
SQUIDsThe dc SQUIDThe rf SQUIDThe SQUID in practice
Type-I and type-II superconductorsCritical fields and vorticesThe Abrikosov latticeCritical current in type-II superconductorsVortex pinning
Superconducting materials
Applications
References
2.3.2.3.1.2.3.2.2.3.3.2.3.4.2.3.5.2.3.6.
3.3.1.3.2.
3.2.1.3.2.2.3.2.3.
3.3.3.3.1.3.3.2.
4.
5.
1.
2.
3.3.1.3.2.
4.4.1.4.2.4.3.4.4.
5.5.1.5.2.5.3
6.6.1.6.2.6.3.6.4.
7.
8.
221221222222223224225
225226227227228228229229230
230
231
232
232
234
235
235
236
237237238
238238239241241
242242244245
246246248249250
251
251
253
XIV
20 - Magnetic thin films and multilayersFrom control of the local environment to control of the physical properties
Preparation and nanostructure of magnetic thin films and multilayersIntroductionExperimental techniques most commonly used to preparemagnetic thin films and multilayers
SputteringMolecular beam epitaxy (MBE)Chemical and structural methods for characterising thin films and multilayers
Magnetism of surfaces, interfaces and thin filmsIncrease in the magnetic moment at the surface of a transition metalSurface magnetism in materials not possessing a moment in the bulkEffects induced by the substrate on the magnetism of ultrathin epitaxic filmsEffect of reduced dimensionality on magnetic phase transitionsMagnetic anisotropy of thin films
Shape anisotropyMagnetocrystalline anisotropyMagnetoelastic anisotropyEffect of roughness and interdiffusion
Coupling mechanisms in magnetic multilayersDirect ferromagnetic coupling by pinholes or by dipolar interactionsCoupling across a non-magnetic film in multilayers consistingof alternating ferromagnetic transition metal and non-magnetictransition or noble metal layers (example Co/Cu)Interfacial coupling between ferromagnetic transition metal films and rare earth films
Transport properties of thin films and multilayersElectronic transport in metals
Classical imageDescription of electrical conductivity in the frameworkof a band model, the free electron gas modelThe two current model, spin dependent scattering in magnetic transition metals
Finite size effect on the conductivity of metallic thin filmsMagnetoresistance in thin films and metallic magnetic multilayers
Anisotropy of the magnetoresistancein ferromagnetic transition metals in bulk and thin film formGiant magnetoresistance (GMR)The physical origin of giant magnetoresistanceDifferent types of giant magnetoresistive multilayers
Spin polarised electron tunnellingApplications of magnetic thin film and multilayers
Magnetic recording mediaMagneto-optical recording mediaSoft materialsMagnetostrictive materialsMaterials for microwave applicationsMagnetoresistive materials
Spin electronics and magnetic nanostructures
References
1.
2.2.1.2.2.
2.2.1.2.2.2.2.2.3.
3.3.1.3.2.3.3.3.4.3.5.
3.5.1.3.5.2.3.5.3.3.5.4.
4.4.1.4.2.
4.3.
5.5.1.
5.1.1.5.1.2.
5.1.3.5.2.5.3.
5.3.1.
5.3.2.5.3.3.5.3.4.
5.4.5.5.
5.5.1.5.5.2.5.5.3.5.5.4.5.5.5.5.5.6.
6.
255
255
258258
259259261263
263264265265266268270270271272
272273
274275
278278278
279281282284
284285287288291295295296297297298298
300
301
XV
21 - Principles of magnetic recordingIntroduction
Overview of the various magnetic recording processesAnalog recordingDigital recordingPerpendicular recordingMagneto-optical recordingDomain propagation memory
Recording mediaParticulate media
Stoner-Wohlfarth modelSuperparamagnetism in particulate media
Granular media, metallic thin filmsContinuous media: epitactic single crystal films and homogeneous amorphous films
The write processField produced by a magnetic headStability of written magnetization patternsWriting a transition with a Karlqvist head
The read processInductive readoutMagnetoresistive readout
Concluding remark
References
22 - FerrofluidsIntroduction
Characteristics of a ferrofluidStabilityTypes of ferrofluids and their production
Surfacted ferrofluidsIonic ferrofluids
Properties of ferrofluidsSuperparamagnetismInteractions between particles: formation of chainsViscosityOptical birefringence
ApplicationsLong-life sealsLubrication - Heat transferPrintingAccelerometers and inclinometersPolishingDampers and shock absorbersApplications of the optical properties of ferrofluidsBiomedical applicationsForeseeable developments
Surface instabilities
References
1.
2.2.1.2.2.2.3.2.4.2.5.
3.3.1.
3.1.1.3.1.2.
3.2.3.3.
4.4.1.4.2.4.3.
5.5.1.5.2.
6.
1.
2.2.1.2.2.
2.2.1.2.2.2.
3.3.1.3.2.3.3.3.4.
4.4.1.4.2.4.3.4.4.4.5.4.6.4.7.4.8.4.9.
5.
305
306
307307310311311312
314314314315316318
318319321323
326326329
335
335
337
337
338338339339340
340340342343344
345345345345345346346346347347
348
351
XVI
OTHER ASPECTS OF MAGNETISM
23 - Magnetic resonance imagingThe physical basis of nuclear magnetic resonance
Energy levels in a magnetic fieldA collection of nuclei in a magnetic fieldRadiofrequency pulsesSpin lattice relaxationFree precession signalChemical shiftSpin echoesThe NMR experiment
Magnetic Resonance ImagingSelective pulses: the linear response approximationField gradientsExcitation of a system of spins in the presence of a gradient: slice selectionImaging: the reciprocal spaceContrast
An example of MRI application: cerebral activation imagingHaemodynamic and blood oxygenation changes induced by neuronal activationBOLD contrast: biophysical mechanisms
Effects of magnetic susceptibility in tissuesSusceptibility effects, and the NMR signal: BOLD contrast
The fMRI sequencesThe fMRI protocol and the processing of the fMR imagesExamples of applications
VisionCognitionMotor function
References
24 - Magnetism of earth materials and geomagnetismIntroduction
Experimental techniquesGeneralitiesMeasurement of remanent magnetization (NRM)Susceptibility and anisotropy measurementsCharacterization of magnetic mineralsMeasurement of magnetic fields
Intrinsic magnetic properties of earth materialsIntroductionMagnetic minerals
OxidesSulphidesOther magnetic mineralsParamagnetic minerals
Applications of magnetic mineralogy to the earth sciences
Magnetic anisotropy: application to the determination of rock fabric
1.1.1.1.2.1.3.1.4.1.5.1.6.1.7.1.8.
2.2.1.2.2.2.3.2.42.5.
3.3.1.3.2.
3.2.1.3.2.2.
3.3.3.4.3.5.
3.5.1.3.5.2.3.5.3.
1.
2.2.1.2.2.2.3.2.4.2.5.
3.3.1.3.2.
3.2.1.3.2.2.3.2.3.3.2.4.
3.3.
4.
355
355355357357358359360361362
362363366367368370
371371373374376380381382382383384
385
387
387
388388389390391392
392392394394396396397397
399
XVII
Natural remanent magnetizationPrinciples of palaeomagnetismNRM acquisition processes
Thermoremanent magnetization (TRM)Crystallization remanent magnetization (CRM)Viscous remanent magnetization (VRM)Detrital remanent magnetization (DRM)Piezoremanent magnetization (PRM)
NRM analysis techniques
Present geomagnetic fieldGeneralitiesCore fieldShort wavelength spatial variations: crustal magnetizationRapid variations: external field
The ancient field recorded by palaeomagnetism
Origin of the core field: dynamo theory
Palaeomagnetic applicationsTectonics and continental driftDating
Extraterrestrial magnetism
References
25 - Magnetism and the Life SciencesMagnetic properties of organic matter
Inert organic materialsLiving organic materialsOrganometallic materials and biology
HemoglobinFerritin and hemosiderinFibrin
Magnetic minerals encapsulated in organic matterAlgae and magnetic bacteriaAnimal magnetismEncapsulated Microspheres
Human sensitivity to magnetic fields
Magnetic exploration techniques for living organismsResonance methodsDetection of magnetic fields produced by living tissuesMagnetic marking techniquesMagnetic sensors
Magnetic techniques for intervention in vivoCardiac valveMagnetic manipulation of cathetersDental careMicro-actuatorsUse of magnetic bacteriaUse of other magnetic materialsMagnetotherapy
Conclusions
References
5.5.1.5.2.
5.2.1.5.2.2.5.2.3.5.2.4.5.2.5.
5.3.
6.6.1.6.2.6.3.6.4.
7.
8.
9.9.1.9.2.
10.
1.1.1.1.2.1.3.
1.3.1.1.3.2.1.3.3.
1.4.1.4.1.1.4.2.1.4.3.
1.5.
2.2.1.2.2.2.3.2.4.
3.3.1.3.2.3.3.3.4.3.5.3.6.3.7.
4.
403403404404404405405405406
407407408409411
413
415
417417420
421
423
425
425425426427427427428428428429429430
431431431432433
433433435436436436437437
438
438
XVIII
26 - Practical magnetism and instrumentationMagnetization measurement techniques
Reciprocity theoremMeasurement of soft materials
Measurement of a toroidal sampleEpstein permeameter
Measurement of the magnetization of hard materials or of weakly magnetic materialsForce methodsFlux methodsHartshorn BridgeMeasurement of anisotropyCalibration of magnetization
Generation of magnetic fieldsMagnetic field generation without using magnetic materials
Calculation of the field produced by a solenoid at any point in spaceThe solenoidSuperconducting coilBitter coilsHybrid techniquesPulsed fields
Generation of magnetic fields using magnetic materialsSome useful approximationsFlux channeling - case of a closed circuitFlux channelingPermanent magnetsAlmost closed U-shaped magnetThe magic cylinder
Measurement of magnetic fieldsHall ProbeFlux gate magnetometer
Reference
APPENDICES
Symbols used in the text
Units and universal constantsConversion of MKSA units into the CGS system, and other unit systems of common use
Some fundamental physical constants
Periodic table of the elements
Magnetic susceptibilities
Ferromagnetic materials
Economic aspects of magnetic materialsIntroduction
Hard materials for permanent magnetsThe applications for magnetsThe main families of permanent magnets
1.1.1.1.2.
1.2.1.1.2.2.
1.3.1.3.1.1.3.2.1.3.3.1.3.4.I.3.5.
2.2.1.
2.1.1.2.1.2.2.1.3.2.1.4.2.1.5.2.1.6.
2.2.2.2.1.2.2.2.2.2.3.2.2.4.2.2.5.2.2.6.
3.3.1.3.2.
1.
2.1.
2.
3.
4.
5.
6.1.
2.2.1.2.2.
441
441441442443444445445447455456456
456457457458458460460461462462463464466468468
469469470
472
475
479
479
480
481
483
487
489
489
490490490
XIX
Bonded magnetsGeographical distribution
Soft materialsSoft ironIron-silicon alloysSpecial alloysHigh frequency materials
Materials for magnetic recording
Other magnetic materialsMagnetostrictive materialsFerrofluids
General references
Index by material
Index by subject
2.3.2.4.
3.3.1.3.2.3.3.3.4.
4.
5.5.1.5.2.
492492
492492493493493
493
494494494
495
497
503
XX
FOREWORD
Thousands of years before our time, our ancestors already knew about the amazingproperties of lodestone, or magnetite. Ever since, man has been fascinated by magneticphenomena, especially because of their action at a distance. They are foundeverywhere in our daily lives: in refrigerator doors, cars, cellphones, suspensionsystems for high speed trains etc. In pure science they are present at all scales, fromelementary particles through to galaxy clusters, not forgetting their role in the structureand history of our Earth.
The last thirty years have seen considerable progress in most of these fields, whetherfundamental or technological. The purpose of this book is to present this progress. Itis the collective work of faculty members and researchers, most of whom work inlaboratories in Grenoble (Universities, CNRS, CEA), often in close cooperation withlocal industry, and the large international organizations established in the Grenoblearea: Institut Laue-Langevin, ESRF (large European synchrotron), etc. This is nosurprise, since activities concerning Magnetism have consistently been supported inGrenoble ever since the beginning of the century.
Most of the chapters are accessible to the University graduate in science. Thosenotions which require a little more maturity do not need to be fully mastered to be ableto understand what comes next. This treatise should be read by all who intend to workin the field of magnetism, such an open-ended field, rich in potential for furtherdevelopment.
New magnets, with higher performance and lower cost, will surely be found. Themagnetic properties of materials containing unfilled electronic shells are not yet fullyunderstood. Hysteresis plays a key role in irreversible effects. While its behavior isfairly well understood both in magnetic fields which are small with respect to thecoercive field, and in very strong fields near saturation, the processes occurring withinthe major loop have not yet been very well described. When hysteresis depends on thecombined action of two variables, such as magnetic field and very high pressure, weknow nothing. How are we, for instance, to predict the magnetic state of a submarinecruising at great depth, depending on its diving course?
French scientists, with Pierre Curie, Paul Langevin and Pierre Weiss, played apioneering role in magnetism. They will certainly have worthy successors, notably inbiomagnetism in a broad sense.
This work includes interesting features: exercises with solutions, referencesfortunately restricted to the best papers and books, and various appendices: lists of
symbols, special functions, properties of various materials, economic aspects, and, lastbut not least, a very necessary summary of units, which the dual coulombic-amperianpresentation made so unnecessarily complicated and unpalatable in the past.
I believe this book should satisfy a broad readership, and be a valuable document tostudents, researchers, and engineers. I wish it a lot of success.
Louis NEELNobel Laureate in Physics,
Member of the French Academy of Science
XXII
PREFACE
Magnetic materials are all around us, and understanding their properties underliesmuch of today’s engineering efforts. The range of applications in which they arecentrally involved includes audio, video and computer technology, telecommunications,automotive sensors, electric motors at all scales, medical imaging, energy supply andtransportation, as well as the design of stealthy airplanes.
This book deals with the basic phenomena that govern the magnetic properties ofmatter, with magnetic materials, and with the applications of magnetism in science,technology and medicine.
It is the collective work of twenty one scientists, most of them from Laboratoire LouisNéel in Grenoble, France. The original version, in French, was edited by Etienne duTrémolet de Lacheisserie, and published in 1999. The present version involves, beyondthe translation, many corrections and complements.
This book is meant for students at the undergraduate and graduate levels in physicsand engineering, and for practicing engineers and scientists. Most chapters includeexercises with solutions.
Although an in-depth understanding of magnetism requires a quantum mechanicalapproach, a phenomenological description of the mechanisms involved has beendeliberately chosen in most chapters in order for the book to be useful to a widereadership. The emphasis is placed, in the part devoted to the atomic aspects ofmagnetism, on explaining, rather than attempting to calculate, the mechanismsunderlying the exchange interaction and magnetocrystalline anisotropy, which lead tomagnetic order, hence to useful materials. This theoretical part is placed, in volume I,between a phenomenological part, introducing magnetic effects at the atomic,mesoscopic and macroscopic levels, and a presentation of magneto-caloric, magneto-elastic, magneto-optical and magneto-transport coupling effects. Volume II, dedicatedto magnetic materials and applications of magnetism, deals with permanent magnet(hard) materials, magnetically soft materials for low-frequency applications, then forhigh-frequency electronics, magnetostrictive materials, superconductors, magnetic thinfilms and multilayers, and ferrofluids. A chapter is dedicated to magnetic recording.The role of magnetism in magnetic resonance imaging (MRI), and in the earth and thelife sciences, is discussed. Finally, a chapter deals with instrumentation for magneticmeasurements. Appendices provide tables of magnetic properties, unit conversions,useful formulas, and some figures on the economic place of magnetic materials.
We will appreciate constructive comments and indications on errors from readers, viathe web site http://lab-neel.grenoble.cnrs.fr/magnetism-book
ACKNOWLEDGMENTS
We are grateful for their helpful suggestions to the members of the ReadingCommittee who worked on the original French edition: V. ARCHAMBAULT (Rhodia-Recherche), E. BURZO (University of Cluj-Napoca, Rumania), I. CAMPBELL
(Laboratoire de Physique des Solides, Orsay), F. CLAEYSSEN (CEDRAT, Grenoble),J.M.D. COEY (Trinity College, Dublin), G. COUDERCHON (Imphy Ugine Précision,Imphy), A. FERT (INSA, Toulouse), D. GIVORD (Laboratoire Louis Néel), L. NEEL,Nobel Laureate in Physics (who passed away at the end of 2000), B. RAQUET (INSA,Toulouse), A. RUDI (ECIA, Audincourt), and P. TENAUD (UGIMAG, St-Pierred’Allevard). The input of many colleagues in Laboratoire Louis Néel or Laboratoired’Electrotechnique de Grenoble was also invaluable: we are in particular gratefulto R. BALLOU, B. CANALS, J. CLEDIERE, O. CUGAT, W. WERNSDORFER. Criticalreading of various chapters by A. FONTAINE, R.M. GALERA, P.O. JUBERT,K. MACKAY, C. MEYER, P. MOLLARD, J.P. REBOUILLAT, D. SCHMITT andJ. VOIRON helped considerably. Zhang FENG-YUN kindly translated a document fromthe Chinese, J. TROCCAZ gave helpful advice in biomagnetism, D. FRUCHART,M. HASSLER and P. WOLFERS provided figures, and P. AVERBUCH gave usefuladvice on the appendix dealing with the economic aspects.
We also would like to thank all our fellow authors for their flawless cooperation inchecking the translated version, and often making substantial improvements withrespect to the original edition. We are happy to acknowledge the colleagues who,along with the two of us, took part in the translation work: Elisabeth ANNE,Nora DEMPSEY, Ian HEDLEY, Trefor ROBERTS, Ahmet TARI, and Andrew WILLS.
We enjoyed cooperating with Jean BORNAREL, Nicole SAUVAL, Sylvie BORDAGE andJulie RIDARD at Grenoble Sciences, who published the French edition and preparedthe present version.
Damien GIGNOUX - Michel SCHLENKER
XXIV