INTRODUCTION TO MAGNETIC MATERIALS

Transcription

1 INTRODUCTION TO MAGNETIC MATERIALS Second Edition B. D. CULLITY University of Notre Dame С D. GRAHAM University of Pennsylvania 4>IEEE PRESS WILEY A JOHN WILEY & SONS, INC., PUBLICATION

2 PREFACE TO THE FIRST EDITION PREFACE TO THE SECOND EDITION xiii xvi 1 DEFINITIONS AND UNITS Introduction / The cgs- emu System of Units / Magnetic Poles / Magnetic Moment / Intensity of Magnetization / Magnetic Dipoles / Magnetic Effects of Currents / Magnetic Materials / SI Units / Magnetization Curves and Hysteresis Loops /18 2 EXPERIMENTAL METHODS Introduction / Field Production By Solenoids / Normal Solenoids / High Field Solenoids / Superconducting Solenoids / Field Production by Electromagnets / Field Production by Permanent Magnets / 36 v

3 VI CONTENTS 2.5 Measurement of Field Strength / Hall Effect / Electronic Integrator or Fluxmeter / Other Methods / Magnetic Measurements in Closed Circuits / Demagnetizing Fields / Magnetic Shielding / Demagnetizing Factors / Magnetic Measurements in Open Circuits / Instruments for Measuring Magnetization / Extraction Method / Vibrating-Sample Magnetometer / Alternating (Field) Gradient Magnetometer AFGM or AGM (also called Vibrating Reed Magnetometer) / Image Effect / SQUID Magnetometer / Standard Samples / Background Fields / Magnetic Circuits and Permeameters / Permeameter / Permanent Magnet Materials / Susceptibility Measurements / 80 Problems / 85 3 DIAMAGNETISM AND PARAMAGNETISM Introduction / Magnetic Moments of Electrons / Magnetic Moments of Atoms / Theory of Diamagnetism / Diamagnetic Substances / Classical Theory of Paramagnetism / Quantum Theory of Paramagnetism / Gyromagnetic Effect / Magnetic Resonance / Paramagnetic Substances / Salts of the Transition Elements / Salts and Oxides of the Rare Earths / Rare-Earth Elements / Metals / General /111 Problems / 113

4 VÜ 4 FERROMAGNETISM Introduction / Molecular Field Theory / Exchange Forces / Band Theory / Ferromagnetic Alloys / Thermal Effects / Theories of Ferromagnetism / Magnetic Analysis / 147 Problems / ANTIFERROMAGNETISM Introduction / Molecular Field Theory / Above 7 N / Below T N / Comparison with Experiment / Neutron Diffraction / Antiferromagnetic / Ferromagnetic / Rare Earths / Antiferromagnetic Alloys / 172 Problems / FERRIMAGNETISM Introduction / Structure of Cubic Ferrites / Saturation Magnetization / Molecular Field Theory / Above T c I Below T c I General Conclusions / Hexagonal Ferrites / Other Ferrimagnetic Substances / y-fe / Garnets / Alloys / Summary: Kinds of Magnetism / 194 Problems / 195

5 MAGNETIC ANISOTROPY Introduction / Anisotropy in Cubic Crystals / Anisotropy in Hexagonal Crystals / Physical Origin of Crystal Anisotropy / Anisotropy Measurement / Torque Curves / Torque Magnetometers / Calibration / Torsion-Pendulum Method / Anisotropy Measurement (from Magnetization Curves) / Fitted Magnetization Curve / Area Method / Anisotropy Field / Anisotropy Constants / Poly crystalline Materials / Anisotropy in Antiferromagnetics / Shape Anisotropy / Mixed Anisotropics / 237 Problems / 238 MAGNETOSTRICTION AND THE EFFECTS OF STRESS Introduction / Magnetostriction of Single Crystals / Cubic Crystals / Hexagonal Crystals / Magnetostriction of Polycrystals / Physical Origin of Magnetostriction / Form Effect / Effect of Stress on Magnetic Properties / Effect of Stress on Magnetostriction / Applications of Magnetostriction / AE Effect / Magnetoresistance / 271 Problems / 272 DOMAINS AND THE MAGNETIZATION PROCESS Introduction / Domain Wall Structure / Neel Walls / 283

6 ix 9.3 Domain Wall Observation / Bitter Method / Transmission Electron Microscopy / Optical Effects / Scanning Probe; Magnetic Force Microscope / Scanning Electron Microscopy with Polarization Analysis / Magnetostatic Energy and Domain Structure / Uniaxial Crystals / Cubic Crystals / Single-Domain Particles / Micromagnetics / Domain Wall Motion / Hindrances to Wall Motion (Inclusions) / Surface Roughness / Residual Stress / Hindrances to Wall Motion (Microstress) / Hindrances to Wall Motion (General) / Magnetization by Rotation / Prolate Spheroid (Cigar) / Planetary (Oblate) Spheroid / Remarks / Magnetization in Low Fields / Magnetization in High Fields / Shapes of Hysteresis Loops / Effect of Plastic Deformation (Cold Work) / 329 Problems / INDUCED MAGNETIC ANISOTROPY Introduction / Magnetic Annealing (Substitutional Solid Solutions) / Magnetic Annealing (Interstitial Solid Solutions) / Stress Annealing / Plastic Deformation (Alloys) / Plastic Deformation (Pure Metals) / Magnetic Irradiation / Summary of Anisotropics / 357

7 X CONTENTS 11 FINE PARTICLES AND THIN FILMS Introduction / Single-Domain vs Multi-Domain Behavior / Coercivity of Fine Particles / Magnetization Reversal by Spin Rotation / Fanning / Curling / Magnetization Reversal by Wall Motion / Superparamagnetism in Fine Particles / Superparamagnetism in Alloys / Exchange Anisotropy / Preparation and Structure of Thin Films / Induced Anisotropy in Films / Domain Walls in Films / Domains in Films / 405 Problems / MAGNETIZATION DYNAMICS Introduction / Eddy Currents / Domain Wall Velocity / Eddy-Current Damping / Switching in Thin Films / Time Effects / Time Decrease of Permeability / Magnetic After-Effect / Thermal Fluctuation After-Effect / Magnetic Damping / General / Magnetic Resonance / Electron Paramagnetic Resonance / Ferromagnetic Resonance / Nuclear Magnetic Resonance / 436 Problems / Soft Magnetic Materials Introduction / Eddy Currents / Losses in Electrical Machines / Transformers / Motors and Generators / 450

8 XI" 13.4 Electrical Steel / Low-Carbon Steel / Nonoriented Silicon Steel / Grain-Oriented Silicon Steel / Six Percent Silicon Steel / General / Special Alloys / Iron-Cobalt Alloys / Amorphous and Nanocrystalline Alloys / Temperature Compensation Alloys / Uses of Soft Magnetic Materials / Soft Ferrites / 471 Problems / HARD MAGNETIC MATERIALS Introduction / Operation of Permanent Magnets / Magnet Steels / Alnico / Barium and Strontium Ferrite / Rare Earth Magnets / SmCo 5 / Sm 2 Co 17 / FeNdB / Exchange-Spring Magnets / Nitride Magnets / Ductile Permanent Magnets / Cobalt Platinum / Artificial Single Domain Particle Magnets (Lodex) / Bonded Magnets / Magnet Stability / External Fields / Temperature Changes / Summary of Magnetically Hard Materials / Applications / Electrical-to-Mechanical / Mechanical-to-Electrical / Microwave Equipment / Wigglers and Undulators / 501

9 XII CONTENTS Force Applications / Magnetic Levitation / 503 Problems / MAGNETIC MATERIALS FOR RECORDING AND COMPUTERS Introduction / Magnetic Recording / Analog Audio and Video Recording / Principles of Magnetic Recording / Materials Considerations / AC Bias / Video Recording / Magnetic Digital Recording / Magnetoresistive Read Heads / Colossal Magnetoresistance / Digital Recording Media / Perpendicular Recording / Possible Future Developments / Magneto-Optic Recording / Magnetic Memory / Brief History / Magnetic Random Access Memory / Future Possibilities / MAGNETIC PROPERTIES OF SUPERCONDUCTORS Introduction / Type I Superconductors / Type II Superconductors / Susceptibility Measurements / Demagnetizing Effects / 525 APPENDIX 1: DIPOLE FIELDS AND ENERGIES 527 APPENDIX 2: DATA ON FERROMAGNETIC ELEMENTS 531 APPENDIX 3: CONVERSION OF UNITS 533 APPENDIX 4: PHYSICAL CONSTANTS 535 INDEX 537