Cullity B.D. Introduction to Magnetic Materials. Second Edition (2008)
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INTRODUCTION TO MAGNETIC MATERIALS
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INTRODUCTION TO MAGNETIC MATERIALS
Second Edition
B.D. CULLITY
University of Notre Dame
C.D. GRAHAM
University of Pennsylvania
Copyright # 2009 by the Institute of Electrical and Electronics Engineers, Inc.
Published by John Wiley & Sons, Inc., Hoboken, New Jersey. All rights reserved.
Published simultaneously in Canada
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Library of Congress Cataloging-in-Publication Data is available:
ISBN 978-0-471-47741-9
Printed in the United States of America
10 9 8 7 6 5 4 3 2 1
CONTENTS
PREFACE TO THE FIRST EDITION |
xiii |
PREFACE TO THE SECOND EDITION |
xvi |
1 DEFINITIONS AND UNITS |
1 |
1.1Introduction / 1
1.2The cgs–emu System of Units / 2
1.2.1Magnetic Poles / 2
1.3Magnetic Moment / 5
1.4Intensity of Magnetization / 6
1.5Magnetic Dipoles / 7
1.6Magnetic Effects of Currents / 8
1.7Magnetic Materials / 10
1.8SI Units / 16
1.9Magnetization Curves and Hysteresis Loops / 18
2 EXPERIMENTAL METHODS |
23 |
2.1Introduction / 23
2.2Field Production By Solenoids / 24
2.2.1Normal Solenoids / 24
2.2.2High Field Solenoids / 28
2.2.3Superconducting Solenoids / 31
2.3Field Production by Electromagnets / 33
2.4Field Production by Permanent Magnets / 36
v
viCONTENTS
2.5Measurement of Field Strength / 38
2.5.1Hall Effect / 38
2.5.2Electronic Integrator or Fluxmeter / 39
2.5.3Other Methods / 41
2.6Magnetic Measurements in Closed Circuits / 44
2.7Demagnetizing Fields / 48
2.8Magnetic Shielding / 51
2.9Demagnetizing Factors / 52
2.10Magnetic Measurements in Open Circuits / 62
2.11Instruments for Measuring Magnetization / 66
2.11.1Extraction Method / 66
2.11.2Vibrating-Sample Magnetometer / 67
2.11.3Alternating (Field) Gradient Magnetometer—AFGM or AGM (also called Vibrating Reed Magnetometer) / 70
2.11.4Image Effect / 70
2.11.5SQUID Magnetometer / 73
2.11.6Standard Samples / 73
2.11.7Background Fields / 73
2.12Magnetic Circuits and Permeameters / 73
2.12.1Permeameter / 77
2.12.2Permanent Magnet Materials / 79
2.13Susceptibility Measurements / 80
Problems / 85
3 DIAMAGNETISM AND PARAMAGNETISM |
87 |
3.1Introduction / 87
3.2Magnetic Moments of Electrons / 87
3.3Magnetic Moments of Atoms / 89
3.4Theory of Diamagnetism / 90
3.5Diamagnetic Substances / 90
3.6Classical Theory of Paramagnetism / 91
3.7Quantum Theory of Paramagnetism / 99
3.7.1Gyromagnetic Effect / 102
3.7.2Magnetic Resonance / 103
3.8Paramagnetic Substances / 110
3.8.1Salts of the Transition Elements / 110
3.8.2Salts and Oxides of the Rare Earths / 110
3.8.3Rare-Earth Elements / 110
3.8.4Metals / 111
3.8.5General / 111
Problems / 113
CONTENTS vii
4 FERROMAGNETISM |
115 |
4.1Introduction / 115
4.2Molecular Field Theory / 117
4.3Exchange Forces / 129
4.4Band Theory / 133
4.5Ferromagnetic Alloys / 141
4.6Thermal Effects / 145
4.7Theories of Ferromagnetism / 146
4.8Magnetic Analysis / 147 Problems / 149
5 ANTIFERROMAGNETISM |
151 |
5.1Introduction / 151
5.2Molecular Field Theory / 154
5.2.1Above TN / 154
5.2.2Below TN / 156
5.2.3Comparison with Experiment / 161
5.3Neutron Diffraction / 163
5.3.1Antiferromagnetic / 171
5.3.2Ferromagnetic / 171
5.4Rare Earths / 171
5.5Antiferromagnetic Alloys / 172
Problems / 173
6 FERRIMAGNETISM |
175 |
6.1Introduction / 175
6.2Structure of Cubic Ferrites / 178
6.3Saturation Magnetization / 180
6.4Molecular Field Theory / 183
6.4.1Above Tc / 184
6.4.2Below Tc / 186
6.4.3General Conclusions / 189
6.5Hexagonal Ferrites / 190
6.6Other Ferrimagnetic Substances / 192
6.6.1g-Fe2O3 / 192
6.6.2Garnets / 193
6.6.3Alloys / 193
6.7Summary: Kinds of Magnetism / 194 Problems / 195
viii CONTENTS
7 MAGNETIC ANISOTROPY |
197 |
7.1Introduction / 197
7.2Anisotropy in Cubic Crystals / 198
7.3Anisotropy in Hexagonal Crystals / 202
7.4Physical Origin of Crystal Anisotropy / 204
7.5Anisotropy Measurement / 205
7.5.1Torque Curves / 206
7.5.2Torque Magnetometers / 212
7.5.3Calibration / 215
7.5.4Torsion-Pendulum Method / 217
7.6Anisotropy Measurement (from Magnetization Curves) / 218
7.6.1Fitted Magnetization Curve / 218
7.6.2Area Method / 222
7.6.3Anisotropy Field / 226
7.7Anisotropy Constants / 227
7.8Polycrystalline Materials / 229
7.9Anisotropy in Antiferromagnetics / 232
7.10Shape Anisotropy / 234
7.11Mixed Anisotropies / 237
Problems / 238
8 MAGNETOSTRICTION AND THE EFFECTS OF STRESS |
241 |
8.1Introduction / 241
8.2Magnetostriction of Single Crystals / 243
8.2.1Cubic Crystals / 245
8.2.2Hexagonal Crystals / 251
8.3Magnetostriction of Polycrystals / 254
8.4Physical Origin of Magnetostriction / 257
8.4.1Form Effect / 258
8.5Effect of Stress on Magnetic Properties / 258
8.6Effect of Stress on Magnetostriction / 266
8.7Applications of Magnetostriction / 268
8.8DE Effect / 270
8.9Magnetoresistance / 271
Problems / 272
9 DOMAINS AND THE MAGNETIZATION PROCESS |
275 |
9.1Introduction / 275
9.2Domain Wall Structure / 276 9.2.1 Ne´el Walls / 283
CONTENTS ix
9.3Domain Wall Observation / 284
9.3.1Bitter Method / 284
9.3.2Transmission Electron Microscopy / 287
9.3.3Optical Effects / 288
9.3.4Scanning Probe; Magnetic Force Microscope / 290
9.3.5Scanning Electron Microscopy with Polarization Analysis / 292
9.4Magnetostatic Energy and Domain Structure / 292
9.4.1Uniaxial Crystals / 292
9.4.2Cubic Crystals / 295
9.5Single-Domain Particles / 300
9.6Micromagnetics / 301
9.7Domain Wall Motion / 302
9.8Hindrances to Wall Motion (Inclusions) / 305
9.8.1Surface Roughness / 308
9.9Residual Stress / 308
9.10Hindrances to Wall Motion (Microstress) / 312
9.11Hindrances to Wall Motion (General) / 312
9.12Magnetization by Rotation / 314
9.12.1Prolate Spheroid (Cigar) / 314
9.12.2Planetary (Oblate) Spheroid / 320
9.12.3Remarks / 321
9.13Magnetization in Low Fields / 321
9.14Magnetization in High Fields / 325
9.15Shapes of Hysteresis Loops / 326
9.16Effect of Plastic Deformation (Cold Work) / 329 Problems / 332
10 INDUCED MAGNETIC ANISOTROPY |
335 |
10.1Introduction / 335
10.2Magnetic Annealing (Substitutional Solid Solutions) / 336
10.3Magnetic Annealing (Interstitial Solid Solutions) / 345
10.4Stress Annealing / 348
10.5Plastic Deformation (Alloys) / 349
10.6Plastic Deformation (Pure Metals) / 352
10.7Magnetic Irradiation / 354
10.8Summary of Anisotropies / 357