Handbook of Magnetic Measurements

398 Pages·2011·13.246 MB·English

by  Slawomir Tumanski

SERIES IN SENSORS

H A N D B O O K O F
MAGNETIC
MEASUREMENTS

S Tumanski

A TAYLOR & FRANCIS BOOK
H A N D B O O K O F
MAGNETIC
MEASUREMENTS
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Warsaw University of Technology
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A TAYLOR & FRANCIS BOOK
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Contents
Preface.........................................................................................................................................................................................ix
Author.........................................................................................................................................................................................xi
Units,Symbols,andConstantsUsedinThisBook...........................................................................................................xiii
1. Introduction to Magnetic Measurements.....................................................................................................................1
2. Fundamentals of Magnetic Measurements..................................................................................................................5
2.1 HistoricalBackground............................................................................................................................................5
2.2 MainTerms...............................................................................................................................................................6
2.2.1 MagneticFieldStrengthH,MagneticFluxΦ,andMagneticFluxDensityB....................................6
2.2.2 MagnetizationM.........................................................................................................................................8
2.2.3 MagneticPolarizationJ..............................................................................................................................8
2.2.4 Permeabilityμ..............................................................................................................................................8
2.2.5 Susceptibilityχ..........................................................................................................................................10
2.2.6 ReluctanceR..............................................................................................................................................10
2.3 TheMagnetizationProcessofFerromagneticMaterials..................................................................................10
2.3.1 DomainStructure.....................................................................................................................................10
2.3.2 MagnetizationCurve................................................................................................................................11
2.3.3 HysteresisLoop.........................................................................................................................................12
2.4 AnisotropyandTexture........................................................................................................................................13
2.4.1 MagnetocrystallineAnisotropy.............................................................................................................13
2.4.2 Texture........................................................................................................................................................16
2.4.3 ShapeAnisotropy.....................................................................................................................................17
2.5 ElectromagneticLoss.............................................................................................................................................19
2.5.1 AxialMagnetizationPowerLoss.............................................................................................................19
2.5.2 PowerLossunderRotationalMagnetization.......................................................................................21
2.6 InfluenceoftheMagneticFieldonPhysicalPropertiesofaMaterial............................................................23
2.6.1 MagnetostrictionandOtherMagnetoelasticEffects...........................................................................23
2.6.2 Magnetoresistance....................................................................................................................................25
2.6.3 Magneto-OpticalPhenomena.................................................................................................................28
2.6.4 MagnetocaloricEffect...............................................................................................................................30
2.7 MagneticResonance..............................................................................................................................................30
2.7.1 GyromagneticRatioandLarmorPrecession........................................................................................30
2.7.2 NuclearMagneticResonance..................................................................................................................32
2.7.3 ElectronSpinResonance...........................................................................................................................34
2.7.4 FerromagneticResonance.........................................................................................................................35
2.7.5 OverhauserResonance.............................................................................................................................36
2.7.6 MössbauerResonance..............................................................................................................................37
2.8 SuperconductivityUsedinMagneticMeasurements......................................................................................38
2.8.1 SuperconductivityandMagnetism—TheMeissnerEffect.................................................................38
2.8.2 JosephsonEffect........................................................................................................................................38
2.8.3 TheSQUIDDevices..................................................................................................................................40
2.8.4 QuantumHallEffect................................................................................................................................41
2.9 MainRulesofMagnetics......................................................................................................................................42
2.9.1 TheBiot–SavartLaw.................................................................................................................................42
2.9.2 Ampère’sCircuitalLaw...........................................................................................................................43
2.9.3 Faraday’sLawofInduction.....................................................................................................................44
2.9.4 LorentzForce.............................................................................................................................................45
2.9.5 Poynting’sVector......................................................................................................................................46
vii
viii Contents
2.9.6 Maxwell’sEquations.................................................................................................................................47
2.9.7 ComputationofaMagneticField...........................................................................................................48
2.10 PhysicalPrinciplesofMagnetism........................................................................................................................51
2.10.1 MagneticFieldandtheMagneticMoment...........................................................................................51
2.10.2 MagneticFieldandBandStructureDensityofStates.........................................................................55
2.10.3 WeakMagnetism—DiamagnetismandParamagnetism...................................................................57
2.10.4 StrongMagnetism—Ferromagnetism...................................................................................................60
2.10.5 MixedMagnetism—AntiferromagnetismandFerrimagnetism.......................................................62
2.10.6 AmorphousandNanocrystallineMaterials.........................................................................................65
2.10.7 MagneticDomainsandDomainWalls.................................................................................................66
2.11 MagneticHysteresis...............................................................................................................................................71
2.11.1 MagnetizationProcess.............................................................................................................................71
2.11.2 RayleighModelofHysteresis..................................................................................................................76
2.11.3 Stoner–WohlfartModelofHysteresis....................................................................................................78
2.11.4 PreisachModelofHysteresis..................................................................................................................80
2.11.5 Jiles–AthertonModelofHysteresis........................................................................................................83
2.11.6 ApproximationoftheMagnetizingCurveandHysteresis................................................................84
2.12 SourcesofaMagneticField..................................................................................................................................85
2.12.1 HelmholtzCoil..........................................................................................................................................85
2.12.2 LongSolenoid............................................................................................................................................87
2.12.3 SourcesofHighMagneticField..............................................................................................................88
2.12.4 SourcesofaMagneticFieldwithArbitraryWaveform......................................................................91
2.13 SamplesandCircuitsoftheMaterialunderTest..............................................................................................93
2.13.1 MeasurementsofBandHValues...........................................................................................................93
2.13.2 RingCore...................................................................................................................................................95
2.13.3 EpsteinFrame............................................................................................................................................97
2.13.4 SingleSheetandSingleStripTesters.....................................................................................................99
2.13.5 SamplesforTwo-DimensionalMeasurements...................................................................................102
2.13.6 OpenSamples..........................................................................................................................................104
2.14 MagneticShielding..............................................................................................................................................105
2.14.1 MagneticFieldPollution........................................................................................................................105
2.14.2 MagneticShielding.................................................................................................................................106
2.14.3 ActiveMagneticShielding—MagneticFieldCancelling..................................................................107
2.14.4 MagneticallyShieldedRoom................................................................................................................108
References........................................................................................................................................................................109
3. Magnetic Materials........................................................................................................................................................117
3.1 SoftMagneticMaterials:GeneralInformation.................................................................................................117
3.1.1 PropertiesandClassification.................................................................................................................117
3.1.2 PureIron...................................................................................................................................................118
3.2 SiliconIronElectricalSteel.................................................................................................................................121
3.2.1 ConventionalGrain-OrientedSiFeSteel.............................................................................................121
3.2.2 HiBGrain-OrientedElectricalSteel.....................................................................................................123
3.2.3 SiFeNon-OrientedElectricalSteel.......................................................................................................126
3.2.4 UnconventionalIron-BasedAlloys......................................................................................................129
3.3 Nickel-andCobalt-BasedAlloys.......................................................................................................................131
3.3.1 NiFeAlloys(Permalloy).........................................................................................................................131
3.3.2 CoFeandCoFeNiAlloys (PermendurandPerminvar).....................................................................134
3.4 AmorphousandNanocrystallineAlloys.........................................................................................................135
3.4.1 AmorphousSoftMagnetic Materials(MetallicGlass)......................................................................135
3.4.2 NanocrystallineSoftMagneticMaterials...........................................................................................137
3.5 SoftFerrites...........................................................................................................................................................140
3.5.1 MnZnandNiZnFerrites.......................................................................................................................140
3.5.2 FerritesforMicrowaveApplications.....................................................................................................141
3.6 HardMagneticMaterials....................................................................................................................................142
Contents ix
3.6.1 GeneralRemarks.....................................................................................................................................142
3.6.2 AlnicoAlloys...........................................................................................................................................146
3.6.3 HardMagneticFerrites..........................................................................................................................146
3.6.4 RareEarthHardMagneticMaterials...................................................................................................147
3.7 SpecialMagneticMaterials..................................................................................................................................149
3.7.1 ThinMagneticFilms..............................................................................................................................149
3.7.2 FerrofluidsandMagnetorheologicalLiquids.....................................................................................155
References........................................................................................................................................................................155
4. Magnetic Sensors...........................................................................................................................................................159
4.1 GeneralRemarks..................................................................................................................................................159
4.1.1 MagneticFieldSensors—Classification..............................................................................................159
4.1.2 SpecificationofthePerformancesofMagneticSensors....................................................................159
4.2 InductionSensors.................................................................................................................................................164
4.2.1 Introduction.............................................................................................................................................164
4.2.2 AirCoilsversusFerromagneticCoreCoils........................................................................................165
4.2.3 DesignoftheAirCoilSensor...............................................................................................................165
4.2.4 DesignofFerromagneticCoreCoilSensor..........................................................................................167
4.2.5 FrequencyResponseofSearchCoilSensor........................................................................................169
4.2.6 ElectronicCircuitsConnectedtotheCoilSensor..............................................................................170
4.2.7 MovingCoilSensor................................................................................................................................172
4.2.8 GradiometerSensor................................................................................................................................172
4.2.9 RogowskiCoil..........................................................................................................................................174
4.2.10 OtherInductionSensors........................................................................................................................175
4.2.10.1 FluxBallSensor.......................................................................................................................175
4.2.10.2 TangentialFieldSensor(H-CoilSensor)..............................................................................175
4.2.10.3 NeedleSensors(B-CoilSensors)............................................................................................176
4.2.11 CoilSensorUsedasaMagneticAntenna...........................................................................................177
4.3 FluxgateSensor....................................................................................................................................................179
4.3.1 PrincipleofOperation............................................................................................................................179
4.3.2 PerformancesofFluxgateSensors........................................................................................................182
4.3.3 DesignofFluxgateSensors...................................................................................................................183
4.3.4 MulticomponentSensorSystems(Compass,Gradiometer)...............................................................185
4.3.5 ElectronicCircuitsofFluxgateSensors...............................................................................................186
4.4 MagnetoresistiveandMagnetoimpedanceSensors.......................................................................................189
4.4.1 Magnetoresistance—GeneralRemarks...............................................................................................189
4.4.2 AMRMagneticFieldSensors................................................................................................................191
4.4.3 MultilayerGMRMagneticFieldSensors............................................................................................197
4.4.4 Spin-ValveGMRMagneticFieldSensors............................................................................................200
4.4.5 Spin-DependentTunnelingGMRMagneticFieldSensors...............................................................204
4.4.6 GiantMagnetoimpedanceSensors......................................................................................................207
4.5 Hall-EffectSensors...............................................................................................................................................213
4.5.1 PhysicalPrinciplesoftheHallEffect...................................................................................................213
4.5.2 DesignofHallSensors............................................................................................................................214
4.5.3 PerformanceoftheHallSensors...........................................................................................................216
4.5.4 IntegratedCircuitHallSensors............................................................................................................218
4.5.5 Hall-Effect-BasedSemiconductorMagnetoresistors.........................................................................218
4.6 SQUIDSensors.....................................................................................................................................................221
4.6.1 OperatingPrincipleofSQUIDSensors...............................................................................................221
4.6.2 DesignandPropertiesofSQUIDSensors...........................................................................................223
4.6.3 SQUIDMagnetometers..........................................................................................................................226
4.7 ResonanceSensorsandMagnetometers..........................................................................................................228
4.7.1 GeneralRemarks.....................................................................................................................................228
4.7.2 NMRMagnetometersforMeasurementsofStrongMagneticFields.............................................229
4.7.3 NMRMagnetometersforMeasurementsofWeakMagneticFields...............................................232
x Contents
4.7.4 OpticallyPumpedSensorsandMagnetometers...............................................................................235
4.7.5 OverhauserMagnetometers..................................................................................................................238
4.8 OtherMagneticSensors......................................................................................................................................240
4.8.1 MagnetoelasticandWiegand-EffectSensors......................................................................................240
4.8.2 OtherandNewPrinciples.....................................................................................................................242
References........................................................................................................................................................................244
5. Testing of Magnetic Materials....................................................................................................................................257
5.1 ACTestingofSoftMagneticMaterials.............................................................................................................257
5.1.1 WhatDoWeUsuallyTest?....................................................................................................................257
5.1.2 StandardTestsofSoftMagneticMaterials.........................................................................................261
5.1.3 Single-SheetandSingle-StripTesters..................................................................................................264
5.1.4 OnlineTestingDevices..........................................................................................................................266
5.1.5 Medium-andHigh-FrequencyTestingofMagneticMaterials.......................................................268
5.1.6 LocalMeasurementsoftheParametersofMagneticMaterials.......................................................271
5.1.7 RotationalPowerLoss............................................................................................................................280
5.1.8 Two-DimensionalProperties................................................................................................................283
5.1.9 AnisotropyandTexture.........................................................................................................................286
5.2 DCTestingofSoftMagneticMaterials.............................................................................................................294
5.2.1 AnalogandDigitalFluxmeters............................................................................................................294
5.2.2 Point-by-PointDCTestingofSoftMagneticMaterials......................................................................298
5.2.3 ContinuousQuasi-StaticTestingofSoftMagneticMaterials..........................................................300
5.2.4 PermeametersforTestingofSoftMagneticMaterials......................................................................301
5.3 TestingofHardMagneticMaterials.................................................................................................................302
5.3.1 TestingoftheHardMagneticMaterialsinClosedMagneticCircuit.............................................302
5.3.2 TestingoftheHardMagneticinOpenMagneticCircuit.................................................................303
5.3.3 PulsedFieldMethods.............................................................................................................................306
5.4 SpecialMethodsofTestingofMagneticMaterials.........................................................................................307
5.4.1 MagnetometricMethods.......................................................................................................................307
5.4.2 MagnetovisionMethod...........................................................................................................................310
5.4.3 OtherScanningSystems.........................................................................................................................316
5.4.4 InvestigationsoftheMagnetostrictionandOtherMagnetomechanicalEffects...........................319
References........................................................................................................................................................................325
6. Magnetic Field Measurements and Their Applications........................................................................................335
6.1 EnvironmentMagneticFields............................................................................................................................335
6.1.1 Earth’sMagneticFields..........................................................................................................................335
6.1.2 TheSpaceResearch................................................................................................................................338
6.1.3 MagneticExplorationandSurveying..................................................................................................341
6.1.4 CompassesandNavigation...................................................................................................................346
6.1.5 ElectromagneticPollution.....................................................................................................................347
6.2 ApplicationsofMagneticFieldMeasurements...............................................................................................351
6.2.1 DetectionofMagneticObjects:MagneticSignature.........................................................................351
6.2.2 MechanicalTransducers........................................................................................................................354
6.2.3 ElectricalTransducers............................................................................................................................359
6.3 MagneticDiagnostics..........................................................................................................................................363
6.3.1 MagneticImaging...................................................................................................................................363
6.3.2 MagneticNondestructiveTesting........................................................................................................369
6.3.3 MagnetisminMedicine.........................................................................................................................373
References........................................................................................................................................................................379
Preface
This book is a continuation of my previous book enti- thiswastheonlysentenceonthesubjectofmagnetism
tled Principles of Electrical Measurement. However, the inthewholethesis!Iwastakenaback.Myastonishment
challengethistimewasmuchmoredifficult.Electrical canbecomparedtothereactionofaFrenchpersonwho
measurements are quite well recognized—there is hasjustlearnedthatallthatistobeknownaboutwines
a lot of good literature on this subject. In the case of is that “they are divided into red and white ones.” It is
magnetic measurements, the availability of up-to-date obvious that similar to wines, magnetic materials are
booksislimited,andinsomepartsIhadtocompilethe represented by hundreds of types, which are further
state-of-the-art knowledge from dispersed specialized divided into hundreds of grades—each with its own
papers. specificproperties.
Of course, there are several excellent books and Magneticdevicesarecommonlyusedinawiderange
review papers concerning magnetic measurements. ofapplications.Thisbookiswrittennotforaspecialist
For many years, we had our “magnetic” bibles, such but rather for a greater audience of engineers and stu-
as Ferromagnetism by Bozorth (first published in 1951), dents with perhaps very little knowledge of “magnetic
Introduction to Magnetic MaterialsbyCullity(1972*),and measurements,” as described in the anecdote above. It
Experimental Methods in Magnetism by Zijlstra (1967). should help them navigate in the jumble of sometimes
Today, however, these books are reprinted mainly as impenetrable terms, but most of all toward the design
historical headstones (maybe also due to the lack of of electromagnetic devices in a more effective way.
moreup-to-datealternatives). Therefore,thisbookbeginswiththeeasy-to-followand
Two modern, excellent books on the subject can be relatively broad topic of “fundamentals of magnetic
recommended as additional readings: Measurement and measurements.” This way, the readers can familiarize
Characterization of Magnetic Materials by Fiorillo and themselves with the essential topics before moving on
Magnetic Sensors edited by Ripka. Both these books, totheotherparts.
however, present rather a relatively narrow part of Specialistsactiveinmagneticmeasurementsdiscuss
the wide spectrum of problems related to magnetic and meet each other at many international confer-
measurements. ences, such as INTERMAG, Soft Magnetic Materials,
In my university, the lecture on magnetic measure- Magnetic Sensors, Magnetic Measurements, and
mentsisnotobligatory.And,indeed,itisverydifficult Workshop on 2D Magnetic Measurements, to mention
to collect a sufficient number of students ready to vol- a few. A large number of “magnetic” papers are pub-
untarilystudythissubjectinmoredetail.Mostofthem lished every year. But for the same reason, this circle
are prejudiced against magnetic measurements after ofadvancedreaderscanoftenbesomewhatadriftand
theprevious(compulsory)lectureonthefundamentals lost in the jungle of information. I hope that this book
of the theory of electricity. In their opinion, magnetic canbehelpfulasanorganizer,guide,andreferencefor
measurements are exceptionally difficult and full of thesereaderstoo.
extremely complex mathematics. Indeed, the Maxwell Magnetic measurements, especially methods of test-
rules; complicated terms such as gradient, divergence, ing of magnetic materials, are quite complex, because
and curl; and the theory of electromagnetic field all many factors, such as the shape of the sample or mag-
require exceptional intellectual effort. For this reason, netizing conditions, influence the results. Therefore,
many students fail to realize that once these difficul- most of the testing methods are precisely described by
ties are overcome, they would be able to recognize the appropriate standards. Unfortunately, despite global-
new fascinating world of science and technology. As a ization,differentcountriesstillusedifferentstandards.
result, the general knowledge of magnetism is rather In this book, I refer to International Electrotechnical
pooramongstudentsand,asaconsequence,practicing Commission(IEC)standardsassumingthatdifferences
engineers. between the main American, European, and Japanese
RecentlyIreviewedadoctoratethesisonpowerelec- standards are not very significant, although, of course,
tronics in which the magnetic part played quite an theycannotbeneglected.
importantpracticalrole.ThePhDstudenthadconcluded Alsotermsandunitsaresometimesdifferentindiffer-
this subject as follows: “In a basic form, the magnetic entcountries.AlthoughtheSIsystem(theInternational
circuitconsistsofamagneticcore,usuallyofferromag- System of Units) is obligatory, in some environments it
netic materials, so-called soft magnetic material.” And is not fully adopted. For instance, physicists still quite
commonlyusetheprevioussystem—Gaussasaunitof
fluxdensity,Oerstedasaunitofmagneticfieldstrength,
*SecondeditionpartiallyupdatedbyGrahamin2009.
xi