MODERN FERRITE TECHNOLOGY SECOND EDITION

Transcription

1 MODERN FERRITE TECHNOLOGY SECOND EDITION

2 MODERN FERRITE TECHNOLOGY SECOND EDITION Alex Goldman Pittsburgh, PA, USA ^ Springer

3 Alex Goldman Ferrite Technology Pittsburgh, PA, USA Modem Ferrite Technology, 2""^ Ed Library of Congress Control Number: ISBN 10: ISBN 13: ISBN 10: (e-book) Printed on acid-free paper Springer Science+Business Media, Inc. All rights reserved. This work may not be translated or copied in whole or in part without the written permission of the publisher (Springer Science+Business Media, Inc., 233 Spring Street, New York, NY 10013, USA), except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed is forbidden. The use in this publication of trade names, trademarks, service marks and similar terms, even if they are not identified as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights. Printed in the United States of America SPIN springeronline. com

4 Dedication This book is dedicated to the memory of Professor Takeshi Takei. Professor Takei, to whom I dedicated the first edition of this 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 (International Conference on Ferrites). Prof. Takei can truly be regarded as the "father of Modern Ferrites". In addition to his pioneering efforts in the early 1930's, he was a guiding light as a teacher of young scientists and engineers and an inspiration to use one's imagination and work hard. He is sorely missed by the whole ferrite community

5 Table of Contents Forward by Takeshi Takei Preface Preface to Second Edition Acknowledgements xi xi xv xiii Chapter 1: Basics of Magnetism Source of Magnetic Effect 1 Introduction 1 Magnetic Fields 1 The Concept of Magnetic Poles 2 Electromagnetism 5 Atomic Magnetism 5 Paramagnetism and Diamagnetism 9 Ferromagnestism 10 Antiferromagnetism 11 Ferrimagnetism 13 Paramagnetism above the Curie Point 14 Summary 14 Chapter 2: The Magnestization in Domains and Bulk Materials 17 Introduction 17 The Nature of Domains 17 Proof of the Existence of Domains 21 The Dynamic Behavior of Domains 23 Bulk Material Magnetization 24 MKSA Units 28 Hysteresis Loops 28 Permeability 30 Magnetocrystalline Anisotropy Constants 31 Magnetostriction 32 Important Properties for Hard Magnetic Materials 33 Summary 34 Chapter 3: AC Properties of Ferrites 35 Introduction 35 AC Hysteresis Loops 35 Eddy Current Losses 35 Permeability 38 Disaccomamodation 42 Core Loss 43 Microwave Properties 44 Microwave Precessional Modes 47 Logic and Switching Properties of Ferrites 48

6 viii MODERN FERRITE TECHNOLOGY Properties of Recording Media 49 Summary 49 Chapter 4: Crystal Structure of Ferrites 51 Introduction 51 Classes of Crystal Structures in Ferrites 51 Hexagonal Ferrites 63 Magnetic Rare Earth Garnets 65 Chapter 5: Chemical Aspects of Ferrites 71 Intrinsic and Extrinsic Properties of Ferrites 71 Magnetic Properties Under Consideration 71 Mixed Ferrites for Property Optimization 72 Temperature Dependence of Initial Permeability 89 Time Dependence Initial Permeability (Disaccomodation) 92 Chemistry Dependence Low Field Losses (Loss Factor) 93 Chemistry Considerations for Hard Ferrites 104 Saturation Induction ^Microwave Ferrites and Garnets 104 Ferrites for Memory and Recording Applications 106 Chapter 6: Microstructural Aspects of Ferrites Introduction Ill Summary 146 Chapter 7: Ferrite Processing 151 Introduction 151 Powder Preparation Raw Materials Selection 151 Nonconventional Processing 163 Nanocrystalline Ferrites 166 Powder Preparation of Microwave Ferrites 174 Hard Ferrite Powder Preparation 175 Chapter 8: Applications and Functions of Ferrites 217 Introduction 217 History of Ferrite Applications 217 General Categories of Ferrite Applications 218 Ferrites at D.C. Applications 219 Power Applications 219 Entertainment Applications 221 High Frequency Power Supplies 223 Microwave Applications 224 Magnetic Recording Applications 224 Miscellaneous Applications 226 Summary 226 Chapter 9: Ferrites for Permanent Magnetic Applications 227 Introduction 227 History of Permanent Magnets 227 General Properties of Permanent Magnets 228 Ill

7 TABLE OF CONTENTS ix Types of Hard Ferrites Materials 232 Criteria for Choosing a Permanent Magnet Material 232 Stabilization of Permanent Magnets 237 Cost Considerations in Permanent Magnet Materials 237 Cost of Finished Magnets 238 Optimum Shapes of Ferrite and Metal Magnets 238 Recoil Lines Operating Load Lines 238 Commercial Oriented and Non Oriented Hard Ferrites 238 Summary 242 Chapter 10: Ferrite Inductors and Transformers for Low Power Applications243 Introduction 243 Inductance 244 Effective Matnetic Parameters 245 Measurements of Effective Permeability 247 Magnetic Considerations: Low-Level Applications 248 Flux Density Limitations in Ferrite Inductor Design 260 Surface Mount Design for Pot Cores 262 Low Level Transformers 262 Ferrites for Low Level Digital Applications 266 ISDN Components and Materials 268 Low Profile Ferritecores for Telecommunications 269 Multi-Layer Chip Inductors and LC Filters 270 Chapter 11: Ferrites for EMI Suppression 273 Introduction 273 The Need for EMI Suppression Devices 273 Materials for EMI Suppression 275 Frequency Characteristics of EMI Materials 278 The Mechanism of EMI Suppression 279 Components for EMI Suppression 281 Differential Mode Filters 286 Chapter 12: Ferrites For Entertainment Applications Radio and TV 291 Introduction 291 Ferrite TV Picture Tube Deflection Yokes 291 Materials for Deflection Yokes 293 Flyback Transformers 297 General Purpose Cores for Radio and Television 299 Ferrite Antennas for Radios 300 Summary 306 Chapter 13: Ferrite Transformers and Inductors at High Power 307 Introduction 307 The Early Power Applications of Ferrites 307 Power Transformers 308 Frequency Voltage Considerations 308 Frequency Loss Considerations 309 The Hysteresis Loop for Power Materials 310

8 X MODERN FERRITE TECHNOLOGY Inverters and Converters 312 Choosing the Right Component for a Power Transformer 313 Choosing the BestFerrite Material 314 Permeability Considerations 318 Output Power Considerations 319 Power Ferrites VS Competing Magnetic Materials 320 Power Ferrite Core Structures 320 Planar Technology 330 High Frequency Applications 324 Determining the Size of the Core 324 Aids in Power Ferrite Core Design 324 Competitive Power Materials for High Frequency 346 Ferroresonant Transformers 347 Power Inductors 348 Chapter 14: Ferrites for Magnetic Recording 353 Introduction 353 Other Digital Magnetic Recording Systems 358 Magnetic Recording Media 361 Magnetic Recording Heads 362 Magnetoresistive Heads 362 Chapter 15: Ferrites for Microwave Applications 375 Introduction 375 The Need for Ferrite Microwave Components 375 Ferrite Microwave Components 376 Commercially Available Microwave Materials 384 Summary 384 Chapter 16: Miscellaneous Ferrite Applications 387 Introduction 387 Summary 393 Chapter 17: Physical, Mechanical and Thermal Aspects of Ferrites 395 Introduction 396 Summary 401 Chapter 18: Magnetic Measurements on Ferrite Materials and Components.403 Introduction 403 Measurements of Magnetic Field Strength 403 Appendix Appendix! 433 Index 435

9 FOREWORD Below is a copy of Professor Takeshi Takei's original preface that he wrote for my first book, Modern Ferrite Technology. 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 have contributed materially to advances in electronics. Research, too, continues apace, 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 the director of the research and development division of Spang & Co. and other enterprises. This book, Modern 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 of today^s most intriguing areas of technology. In the first part of the 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

10 xii MODERN FERRITE TECHNOLOGY frequencies. He uses anisotropy and fme 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 pose from a design point of view in actual applications. Turning to the subject of magnetic recordings, 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 listings of the latest physical, chemical and magnetic data available on ferrites and listings of world 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 the author 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

11 Preface to Second Edition A number of years have passed since the first edition of Modern Ferrite Technology was published. Four ICF's (International Conference on Ferrites) have taken place since then ie.l992 (Kyoto), 1996 (Bordeaux), 2000 (Kyoto) and 2004 (San Francisco). During that time, so many significant events have occurred in the field of ferrites that the author was prompted to undertake an updating and expansion of the material in the first edition. In the area of new materials, ferrites with permeabilities of 20,000 and 30,000 have been made available commercially, albeit only in small toroids, but still an impressive accomplishment. In addition, power ferrites which have expanded greatly during this time have now been available for frequencies up to 3 MHz. in MnZn ferrites and to 10 MHz. for NZn ferrites. In the field of ceramic processing, the whole area of nanostructured ferrites has come roaring in and while commercial utilization of these materials have not full been exploited to date, the scientific work has been outstanding. In the area of ownership and geographical changes in location of commercial ferrite manufacturers, the scene has changed dramatically. Companies such as Siemens, Philips and Thomson CSF. Have had ownership changes. The geographical center for large scale ferrite production has changed from Japan where it was 30 years ago to China which, it is estimated to have about 60-70% of the world's ferrite proction in the late 2000's. In addition to these new factors, the author has also inserted several new chapters on ferrite applications not covered in the first edition. They are; 1. Ferrites for EMI Suppression Applications 2. Ferrites for Entertainment Applications 3. Ferrites for Magnetic Recording 4. Ferrites for Microwave Applications 5. Ferrite Functions and Applications The new edition of the book is divided into two parts, the first describing the properties and processing of ferrites and the second part on the functions and applications of ferrites. The chapters on chemistry, microstructure have been expanded to accommodate the new findings. The section on component design have been minimized but section on design aids such as networking have been included. In the first edition of Modern 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. In expanding my earlier book. Modern 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 of ICF6 and ICF7, ICF8 and ICF9 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).

12 xiv MODERN FERRITE TECHNOLOGY 3. To add chapters on magnetic materials of expanding importance, such as those for EMI 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 ferrite 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.. 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 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 EMI and entertainment uses. Finally we come to the very large and important chapter on high frequency power materials and components. 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 lec 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

13 ACKNOWLEDGEMENTS ACKNOWLEDGEMENTS I would like to thank Joseph F. Huth III 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. Richard Parker and Mr. John Knight of Fair-Rite products also provided me with important information on EMI and permanent magnet materials. I would also like to thank the people at Fair-Rite Products, Steward, Arnold Engineering, Magnetics, TDK and FDK for their catalog data. I would like thank Prof.M. Sugimoto for the material from ICF6, ICF7, ICF8 and ICF9. 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.