HANDBOOK OF MODERN FERROMAGNETIC MATERIALS

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1 HANDBOOK OF MODERN FERROMAGNETIC MATERIALS

2 THE KLUWER INTERNATIONAL SERIES IN ENGINEERING AND COMPUTER SCIENCE

3 HANDBOOK OF MODERN FERROMAGNETIC MATERIALS Alex Goldman, B.S., A.M., Ph.D. Ferrite Technology Worldwide w Springer Science+Business Media, LLC

4 Library of Congress Cataloging-in-Publication Data Goldman, Alex. Handbook of modern ferromagnetic materials / Alex Goldman, p. cm. ~ (The Kluwer international series in engineering and computer science ; SECS 505) Includes bibliographical references. ISBN ISBN (ebook) DOI / Magnetic materials. 2. Electronics-Materials. 3. Ferrites (Magnetic materials) I. Title. II. Series. TK M3G dc CIP Copyright 1999 by Springer Science+Business Media New York Originally published by Kluwer Academic Publishers in 1999 Softcover reprint of the hardcover 1st edition 1999 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher, Springer Science+Business Media, LLC Printed on acid-free paper.

5 Dedication This book is dedicated to the memory of tbree men who greatly influenced the scientific life of the author, Professor Takeshi Takei, Dr. Richard M Bozorth and Dr. Gilbert Y. Chin. Professor Takei, to whom I dedicated my first book and whose preface to that book follows this dedication, was a greatly loved friend and teacher of mine. He passed away on March 12, He will be remembered as a founding father of ferrites, a great teacher and the organizer of ICF(lntemational Conference on Ferrites).. Since the present book includes chapters on metallic magnetic materials, the contributions of both Dr. RichaId M Bozorth and Dr. Gilbert Y. Chin are also remembered Richard M Bozorth was head of the Magnetics Research Department at the Bell Telephone Laboratories in Murray Hill, New Jersey for many years. His book,. "Ferromagnetism" is probably the most important reference book on the subject. Dr. Gilbert Y. Chin was a dear friend of mine whose untimely death was a great blow to me and the world of magnetics. He was responsible for my trip to the Peoples Republic of China to discuss magnetic materials processing. The scientific community has been well served by the lives of these tbree men.

6 TABLE OF CONTENTS Foreword by Takeshi Takei Preface Acknowledgements xv xvii xix Chapter I-Applications and Functions of Ferromagnetic Material 1 What are Ferromagnetic Materials? 1 History of Ferromagnetic Materials 1 General Categories of Magnetic Materials 2 Applications of Magnetic Materials at DC 4 Power Applications at Low Frequencies 5 Low Frequency Transformers 6 Entertainment Applications 9 High Frequency Power Supplies 11 Microwave Applications 12 Magnetic Recording Applications 13 Miscellaneous Applications 14 Chapter 2-Basics of Magnetism-Source of Magnetic Effect 17 Magnetic Fields 17 Electromagnetism 21 Atomic Megnatism 21 Paramagnetism and Diamagnetism 26 Paramagnetism of Metals 27 Ferromagnetism 29 Magnetic Moments in Ferromagnetic Metals and Alloys 32 Antiferromagnetism 34 Ferrimagnetism 39 Chapter 3-The Magnetization in Domains and Bulk Materials 41 The Nature of Domains 41 Proof of the Existence of Domains 47 The Dynamic Behavior of Domains 47 Bulk Material Magnetization 48 Hysteresis Loops 53 Permeability 54 Magnetocrystalline Anisotrophy Constants 55 Magnetostriction 57 Important Properties for Hard Magnetic Materials 57

7 viii HANDBOOK OF MODERN FERROMAGNETIC MATERIALS Chapter 4-AC Properties of Magnetic Materials 59 AC Hysteresis Loops 59 Eddy Current Losses 59 Permeability 62 Disaccomodation 66 Core Loss 68 Microwave Properties 69 Microwave Precessional Modes 71 Logic and Switching Properties offerrites 72 Properties of Recording Media 73 Chapter 5-Materials for Permanent Magnet Applications 75 History of Permanent Magnet 75 General Properties of Permanent Magnets 78 Commercial Permanent Magnet Materials-Properties 81 Oxidic or Hard Ferrite Materials 86 Commercial Oriented and Non-Oriented Hard Ferrites 86 Rare-Earth-Cobalt Permanent Magnet Materials 90 Neodymium-Iron-Boron Permanent Magnet Materials 92 Iron-Chromium-Cobalt Magnet Materials 95 Ductile Permanent Magnet Alloys 95 Miscellaneous Permanent Magnet Materials 95 Criteria for Choosing a Permanent Magnet Material 95 Stabilization of Permanent Magnets 100 Cost Considerations in Permanent Magnet Materials 100 Cost of Finished Magnets 101 Calculations and Design of Magnets 102 Optimum Shapes of Ferrite and Metal Magnets 106 Recoil Lines-Opel3ting Load Lines 106 Chapter 6-DC and Low Frequency ApplicatioDII 107 Material Requirements for DC and Low Frequencies 107 Metallic Materials for DC or Low Frequencies 108 Soft Iron as a Magnetic Material 110 Low Carbon Steels 112 Silicon Steels 115 lron-based Amorphous Materials 122 Other Low-frequency Magnetic Alloys 127 Nanocrystalline Materials 130 Sintered Soft Iron for Magnetic Applications 130 Chapter 7-Soft Cobalt-Iron Alloys 137 History ofiron-cobalt Alloys 137 Chemistry and Structure of Cobalt-Iron Alloys 137

8 TABLE OF CONTENTS ix Commercial Availability of Soft Cobalt-Iron Alloys Applications of Soft Cobalt-Iron Alloys Magnetic Components Using Cobalt-Iron Alloys Chapter 8-Metallic Materials for Magnetic Shielding Applications. Shielding Factor and Attenuation Materials for Magnetic Shielding Processing of Shield Materials Measurement of Shield Material Commercial Forms of Supply Shielding Factor as a Function of Frequency Chapter 9-High Permeability-High Frequency Metal Strip History of Nickel-Iron Alloys High Permeability Nickel-Iron Alloys Binary Nickel-Iron Alloys in the 80% Ni Range Nickel-Iron Alloys with 65% Nickel Nickel-Iron Alloys in the 36% Nickel Range Amorphous Materials-High Penn-HigbFrequency Nanocrystalline Materials-High Frequency Operation Chapter 10-Metal Powder Cores for Telecommunications History of Powder Cores for Telecommunications Iron Powder Cores for Audio and RF Applications Processing of Iron Powder Cores Moly-Perm Powder Cores for Telecommunications Properties of Moly-Perm Powder Cores Chapter U-Crystal Structure of Ferrites Classes of Crystal Structures in Ferrites Normal Spinels Inverse Spinels Magnetic Moments in Inverse Spinels Mixed Zinc Ferrites Sublattice Magnetizations Hexagonal Ferrites Magnetic Rare-Earth Garnets Miscellaneous Structures Chapter 12-Chemical Aspects of Ferrites Intrinsic and Extrinsic Properties of Ferrites Mixed Ferrites for Property Optimization Permeability Dependence on Chemistry lsi

9 x HANDBOOK OF MODERN FERROMAGNETIC MATERIALS Effect of Iron Content on Permeability 232 Effect of Divalent Ion Variation 236 Permeability Dependence on Zinc 238 Effect of Cobalt on Permeability 239 Oxygen Stoichiometry 240 Effect of Purity on Permeability 244 Effect of Foreign Ions on Permeability 245 Temperature Dependence oflnitial Permeability 247 Time Dependence of Permeability (Disaccomodation) 250 Chemistry Dependence of Low Field Losses Loss Factor 251 Tetravalent and Pentavalent Oxide Substitution 251 Losses at High Power Levels 256 Chemistry Considerations for Hard Ferrites 259 Saturation Induction of Microwave Ferrites and Garnets 260 Chemistry Dependence of Microwave Properties 261 Ferrites for Memory and Recording Applications 262 Chapter 13-Microstl1lctural Aspects of Ferrites 265 Microstructural Engineering for Desired Properties 265 The Effects of Grain Size on Permeability 266 Exaggerated Grain Growth in Ferrites 268 Duplex Grain Structures 271 Effect of Porosity on Permeability 271 Separation of Grain Size and Porosity Effects 273 Effect of Grain Size and Porosity on B-H Loop Panuneters 276 Grain Boundary Considerations 279 Early Studies of Grain Boundaries 280 High Frequency Materials 284 Considerations of Microstructure for Microwave Ferrites 291 Microstructural Considerations of Hard Ferrites 292 Resistive and Capacitive Effects in Grain Boundaries 293 Phase Transformation and Oxidation 299 Chapter 14-Ferrite Processing 305 Powder Preparation-Materials Selection 305 Weighing and Blending 309 Calcining 310 Milling 313 Granulation or Spay DIying 313 Pressing 314 Non-conventional Processing 317 Powder Preparation of Microwave Ferrites 325 Hard Ferrite Powder Preparation 325 Sintering Spinel Ferrites 326 Sintering Manganese-Zinc Ferrites 328

10 TABLE OF CONTENTS xi Hold or Soak Temperature and Duration Atmosphere Effects Sintering ofmnzn Ferrites for Specific Applications Power Ferrites Microstructural Development Ferrite Kilns Firing of Microwave Ferrites and Garnets Firing of Hard Ferrites Finishing Operations for Ferrites Ferrite and Gamet Films Single Crystal Ferrites Chapter IS-Ferrite Inductors and Transformers for Low Power Inductance Effective Magnetic Parameters Measurement of Effective Permeability Magnetic Considerations:Low Level Applications Pot Core Assembly Pot Core Shapes and Sizes Designing for Inductance in Pot Cores Designing a Pot Core Inductor for Maximum Q Designing Ferrite Inductors for Stability Requirements Flux Density Limitations in Ferrite Inductor Design DC Bias Effects in Ferrite Inductor Design Surface-Mount Design for Pot Cores Low Level Transformers Ferrite Pulse Transformers Ferrites for Low-Level Digital Applications ISDN Components and Materials Multilayer Chip Inductors and LC Filters Chapter 16-Soft Magnetic Materials for EMI Suppression The Need for EMI Suppression Devices Materials for EMI Suppression Frequency Characteristics of EMI Materials Mechanism of EMI Suppression Components for EMI Suppression Common-Mode Filters Differential Mode Filters Metal Powder Cores for EMI Suppression Amorphous-Nanocrystalline Materials for EMI Suppression Chapter 17-Ferrites for Entertainment Applications

11 xii HANDBOOK OF MODERN FERROMAGNETIC MATERIALS Ferrite TV Picture Tube Deflection Yokes 425 Materials for Deflection Yokes 427 Flyback Transformers 430 General Purpose Cores for Radio and Television 433 Ferrite Antennas for Radio 434 Chapter 18-Ferrite Transformers and Inductors at High Power 441 The Early Power Applications offerrites 441 Power Transformers 442 Frequency-Voltage Considerations 442 Frequency-Loss Considerations 443 The Hysteresis Loop For Power Materials 444 Inverters and Converters 446 Choosing the Right Component for a Power Transformer 453 Permeability Considerations 459 Limitations in Ferrite Design 460 Output Power Considerations 462 Power Ferrites vs Competing Magnetic Materials 465 Power Ferrite Core Structures 465 Low Profile Ferrite Power Cores 467 Surface-Mount Design in Power Ferrites 470 Core Geometries 470 Planar Technology 479 High Frequency Applications 482 Design of Ferrite a Component for Power Transformers 482 Determining the Size of the Core 485 Voltage Regulation in Transformers 490 Other Transformer Design Techniques 492 Magnetic Amplifier-Multi Output Design 496 Power Ferrite Design from Vendor's Catalogs 497 Computer-Aided Power Transformer Design 501 Winding Losses 502 Completing the Design of the Transformer-Winding Data 503 Very High Frequency Power Ferrite Operation 504 Competitive Power Materials for High Frequencies 507 Ferroresonant Transformers 507 Power Inductors 509 Ferrite vs Metallic Power Inductor Materials 510 Flyback Converter Design 521 Swinging Choke 522 Appendices 522 Chapter 19-Materials for Magnetic Recording 535 History of Magnetic Recording 535

12 TABLE OF CONTENTS xiii Magnetic Recording Head Properties Audio and Video Magnetic Recording Magnetic Recording Media Magnetic Recording Heads Magnetoresistive Heads Magneto-optic Recording Outlook for Areal Densities in Magnetic Recording Chapter 20-Ferrites for Microwave Applications The Need for Ferrite Microwave Components Ferrite Microwave Components Commercially-Available Microwave Materials Chapter 21-MisceUaneous Magnetic Material Applications Magnetostrictive Transducers Sensors Copier Powders Ferrotluids Electrodes Delay Lines Ferrite Tiles for Anechoic Chambers Reed Switches Chapter 22-Physical-Thermal Aspects of Magnetic Materials Densities offerrites Mechanical Properties offerrites Thermal Properties Pressure Effects on Ferrites Radiation Resistance Chapter 23-Magnetic Measurements-Materials and Components Measurement of Magnetic Field Strength Measurement of Magnetization Magnetization Curves and Hysteresis Loops Measurements on Hard Ferrites Magnetocrystalline Anisotropy Magnetostriction Inductance and Permeability Measurements Loss Factor QFactor High Frequency Measurements Permeability Measurements on Ferrite Components Loss Separation at Low Flux Density

13 DV HANDBOOK OF MODERN FERROMAGNETIC MATERIALS Losses at High Power Levels-Core Losses 608 Pulse Measurements 615 Amplitude Permeability 615 Bibliography 623 Appendix I-Abbreviations and Symbols 627 Appendix 2-List of World's Major Ferrite Suppliers 633 Appendix 3-Units conversion from CGS to MKS(SI) System 641 Index 643

14 FOREWORD Below is a copy of Professor Takeshi Takei's original preface that he wrote for my first book, Modem Ferrite Teclmology. I was proud to receive this preface and include it here with pride and affection. We were saddened to learn of his death at 92 on March 12, Preface It is now some 50 years since ferrites debuted as an important new category of magnetic materials. They were prized for a range of properties that had no equivalents in existing metal magnetic materials, and it was not long before full-fledged research and development efforts were underway. Today, ferrites are employed in a truly wide range of applications, and the efforts of the many men and women working in the field are yielding many highly intriguing results. New, high-performance products are appearing one after another, and it would seem we have only scratched the surface of the hidden possibilities of these fascinating materials. Dr. Alex Goldman is well qualified to talk about the state of the art in ferrites. For many years Dr. Goldman has been heavily involved in the field as director of the research and development division of Spang & Co. and other enterprises. This book, Modem Ferrite Technology, based in part on his own experiences, presents a valuable overview of the field. It is testimony to his commitment and bountiful knowledge about one oftoday's most intriguing areas of technology. In the first part of his book, Dr. Goldman discusses the static characteristics of ferrites based on the concept of ferrimagnetism. He then considers their dynamic properties in high-frequency magnetic fields. Dr. Goldman follows this up with a more detailed look at some of these characteristics. In a section on power materials he examines the need to use chemical adjustment and microstructural optimization to attain high saturation and low core loss at high frequencies. He uses anisotropy and fine particle concepts to describe permanent magnetic ferrites and reviews how gyromagnetic properties help explain the actions of microwave ferrites. In a section on applications, he introduces such production technologies-some conventional, some unconventional-as coprecipitation, spray roasting and single crystal preparation. He also discusses some of the special difficulties that ferrites can impose from a xv

15 xvi HANDBOOK OF MODERN FERROMAGNETIC MATERIALS design point of view in actual applications. Turning to the subject of magnetic recording, Dr. Goldman discusses in detail the impressive strides being made in magnetic media and magnetic head applications. The book is rounded out with valuable appendices, including a list of the latest physical, chemical and magnetic data available on ferrites and listings ofworld ferrite suppliers. Modern Ferrite Technology presents the reader with the latest thinking on ferrites by the scientists, researchers and technicians actually involved in their development, leavened with the rich experiences over many years of theauthor himself. It is a work of great interest not only to those researching new ferrite materials and applications, but to all in science and industry who use ferrites in their work. April 1987 Takeshi Takei

16 Preface It bas been almost fifty years since Dr. Richard M Bozorth wrote his landmark book. "Ferromagnetism". This book has been considered by many (including the author) to be the "Bible" of ferromagnetic materials. Evidence for its popularity has been shown by the fact that the IEEE in 1993, some 40 years after its original publication, reissued the book In my present book. I have liberally referenced from Dr. Bozorth's book for several reasons. First, many of the basic concepts on ferromagnetism have not changed much since then. A number of the materials discussed in Bozorth's book such as 4-79 Permalloy strip and 2-81 Moly-perm powder cores are still being used in pretty much the same form. Second, Bozorth's book presents a bench mark or comparision for so many of the newer materials including ferrites, amorphous materials and of course, the newest nanocrystalline materials. In my earlier book. Modem Ferrite Technology, I remarked that ferrites were ''the new kids on the block". Well, by now, the kids have turned into teenagers and, as such, are making their presence felt. However, they are being challenged by a new breed of metallic materials including the non-crystalline amorphous alloys and the magnetic nanocrysta1line materials. How could Bozorth have dreamed of such revolutionary materials and such amazing techniques such as nwltilayer films so important in magnetic recording? As a matter of fact, in Bozorth's book. ferrites barely got six pages in his volume of nearly 1000 pages. In expanding my earlier book. Modem Ferrite Technology, I am attempting to accomplish several objectives; 1. To update the information on ferrites to include the advances since the original work including the major features oficf6 and ICF7. 2. To provide a method of comparison of the main features of all the commercially available ferromagnetic materials (and some that are not available such as the Colossal Magnetoresistive Materials). 3. To add chapters on magnetic materials of expanding importance, such as those for EM! suppression and for entertainment applications 4. To introduce the magnetic materials and components for new technologies such as ISDN, planar magnetics, surface-mount techniques, magnetoresistive recording and integrated magnetics. As I wrote in the preface in my first book. the attempt here is to describe in as non-technical language as possible, the material, magnetic, and stability characteristics of a wide variety of materials. These materials are introduced in chapters according to frequency. In this scheme, we would then start with the lowfrequency metallic power materials, continue to the higher permeability and higher frequency strip materials, to the metal powder cores and finally to ferrites at the highest frequencies including microwaves. xvii

17 xviii HANDBOOK OF MODER.~ FERROMAGNETIC MATERIALS The book is aimed at several different audiences. The first chapter takes a broad view of all the applications and functions of magnetic materials. This chapter would appeal to somebody just getting his or her feet wet in the Sea of Magnetism without getting into the materials themselves. The next three chapters are also introductory in nature and deal with the basic concepts of origins of magnetic phenomena, domain and magnetization behavior, magnetic and electrical units and finally to the the action of magnetic materials under ac drive. Then come the sections on the materials themselves, starting with the DC applications and specifically the permanent magnet materials. The first is one of the few chapters in which metallic and non-metallic materials are discussed together for comparison purposes. The next chapter involves the metallic strip materials for line or mains (50-60 Hz. ) power including a discussion of some of the new sintered iron alloys. Slightly higher ( Hz. ) frequencies are dealt with in the next chapter on the cobaltiron alloys. The next chapter deals with materials for magnetic shielding for protection of sensitive devices. Some of the same materials appear in the next chapter dealing with the high permeability and higher frequency materials, including the nickel-iron alloys and the amorphous metals. We then leave the metal strip materials and go to the powdered metal materials which are useful at the higher frequencies. We then shift to the ferrite materials and the next three chapters deal with the material properties including crystal structure, chemistry and microstructure. These sections are then followed by a chapter on processing of ferrites. The first part of this book (14 chapters) has dealt mainly with the material science aspects of ferromagnetism. Most of the rest of the book is involved with the specific applications. First, we will try to make use of the special properties of the materials we have studied in the low power or telecommunication area, then the associated EM! and entertainment uses. Finally we come to the very large and important chapter on high frequency power materials and components. Although many of the materials in these chapters are ferrites, in these cases, competing materials are introduced to enable the design engineer to make the best choice based on quality, stability and cost. The next chapter discusses the materials for magnetic recording. The sections on magnetoresistive and magneto-optical recording have been expanded to include the new developments. The next chapter deals with the materials for microwave applications and the last application section is on miscellaneous materials that includes materials for theft deterrence and anechoic chamber tiles. The final chapters discuss the mechanical and thermal aspects ending with a chapter on magnetic measurements. A listing of the IEC and ASTM documents appear at the end of this chapter. The appendices include abbreviations and symbols, listing of major ferrite suppliers of the world and units conversion from cgs to MKS. As I described in the preface to the earlier book, I would hope that this book also provides a bridge between the material scientist and the electrical design engineer so that some common ground can be established and an understanding of the problems of each can be gained. Alex Goldman

18 ACKNOWLEDGEMENTS Dx I would like to thank Joseph F. Huth ill and Harry Savisky of the Magnetics Div. of Spang and Co. for providing me with some of the photos, photomicrographs and figures in the book. Mr. John Knight of Fair-Rite products also provided me with important information on permanent magnet materials. I would also like to thank the people at Fair-Rite Products, Steward, Allied Signal, Vacuumschmelze, Arnold Engineering, Magnetics, Micrometals, TDK, MMG-North America, Cartech Pyroferric and FDK for their catalog data. I would like thank Prof.M. Sugimoto for the material from ICF6 and 7. Finally, I would like to thank my wife, Adele, who put up with my endless hours at the computer with great love and understanding and also to my children, Drs. Mark, Beth and Karen for lots of pride and inspiration that they have given to me.

MODERN FERRITE TECHNOLOGY SECOND EDITION

MODERN FERRITE TECHNOLOGY SECOND EDITION MODERN FERRITE TECHNOLOGY SECOND EDITION Alex Goldman Pittsburgh, PA, USA ^ Springer Alex Goldman Ferrite Technology Pittsburgh, PA, USA Modem Ferrite Technology,