Modern Permanent Magnets

Modern Permanent Magnets

1st Edition - January 27, 2022

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  • Editors: John Croat, John Ormerod
  • Paperback ISBN: 9780323886581
  • eBook ISBN: 9780323886406

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Modern Permanent Magnets provides an update on the status and recent technical developments that have occurred in the various families of permanent magnets produced today. The book gives an overview of the key advances of permanent magnet materials that have occurred in the last twenty years. Sections cover the history of permanent magnets, their fundamental properties, an overview of the important families of permanent magnets, coatings used to protect permanent magnets and the various tests used to confirm specifications are discussed. Finally, the major applications for each family of permanent magnets and the size of the market is provided. The book also includes an Appendix that provides a Glossary of Magnetic Terms to assist the readers in better understanding the technical terms used in other chapters. This book is an ideal resource for materials scientists and engineers working in academia and industry R&D.

Key Features

  • Provides an in-depth overview of all of the important families of permanent magnets produced today
  • Includes background information on the fundamental properties of permanent magnets, major applications of each family of permanent magnets, and advances in coatings and coating technology
  • Reviews the fundamentals of permanent magnet design


Materials Scientists and Engineers. Electrical Engineers, Automotive Engineers

Table of Contents

  • Cover Image
  • Title Page
  • Copyright
  • Table of Contents
  • Contributors
  • Chapter 1 The history of permanent ­magnets
  • Abstract
  • 1.1 Introduction
  • 1.2 Lodestones: the first permanent magnets
  • 1.3 Early permanent magnet studies
  • 1.4 The era of steel permanent magnets
  • 1.5 The discovery of alnico permanent magnets
  • 1.6 The discovery of hard ferrite magnets
  • 1.7 The discovery of Sm-Co permanent magnets
  • 1.8 The discovery of NdFeB permanent magnets
  • 1.9 The discovery of Sm-Fe-N permanent magnets
  • 1.10 Future permanent magnet materials
  • 1.11 Summary
  • References
  • Chapter 2 Fundamental properties of permanent magnets
  • Abstract
  • 2.1 Introduction
  • 2.2 The different families and types of permanent magnets
  • 2.3 Key magnetic parameters
  • 2.4 On the origin of magnetism
  • 2.5 The different types of magnetism
  • 2.6 The origin of anisotropy in permanent magnets
  • 2.7 Magnetic domains and domain walls
  • 2.8 Magnetic hysteresis
  • 2.9 Coercivity mechanism in modern permanent magnets
  • 2.10 Stability of permanent magnets
  • References
  • Chapter 3 Recent advances in hard ­ferrite magnets
  • Abstract
  • 3.1 Introduction
  • 3.2 Historical overview of M-type Sr- and Ba- Hexaferrites
  • 3.3 Crystal structure, intrinsic magnetic properties, microstructure and morphology
  • 3.4 Advances towards the improvement of intrinsic magnetic properties
  • 3.5 Industrial fabrication routes
  • 3.6 Recycling efforts, recovery, and reusability in production line
  • 3.7 Applications of hexaferrites: present and perspectives
  • References
  • Chapter 4 Modern Sm-Co permanent magnets
  • Abstract
  • 4.1 Introduction
  • 4.2 Manufacturing process of Sm-Co magnets
  • 4.3 High (BH)max Sm2Co17 type permanent magnets
  • 4.4 Temperature compensated Sm-Co magnets
  • 4.5 Ultra-high temperature Sm-Co magnets with small reversible temperature coefficient of Br
  • 4.6 Performance of Sm-Co magnets in special environments
  • 4.7 Laminated Sm-Co magnets
  • 4.8 Additive manufacturing
  • 4.9 Small magnets
  • 4.10 Sm-Co nanoparticles and nanoflakes for nanocomposite magnets
  • 4.11 Summary
  • References
  • Chapter 5 The status of sintered NdFeB magnets
  • Abstract
  • 5.1 Introduction
  • 5.2 History of the development of Nd-Fe-B
  • 5.3 Compositions of the NdFeB sintered magnets and their magnetic properties
  • 5.4 Production process for sintered NdFeB magnets
  • 5.5 Progress in the microstructure investigation
  • 5.6 Development of HRE-Free and reduced HRE magnets
  • 5.7 Ultimate NdFeB sintered magnets for EV traction motors
  • References
  • Chapter 6 Compression bonded NdFeB permanent magnets
  • Abstract
  • 6.1 Introduction
  • 6.2 The compression molding process
  • 6.3 Isotropic compression bonded NdFeB permanent magnets
  • 6.4 Anisotropic hot deformed NdFeB compression bonded magnets
  • 6.5 Compression molded HDDR permanent magnets
  • References
  • Chapter 7 Injection molded permanent magnets
  • Abstract
  • 7.1 Introduction
  • 7.2 Overview of applications, basic parameters and materials
  • 7.3 Manufacturing
  • 7.4 Polarization patterns
  • 7.5 Design of in-mold magnetized magnets
  • 7.6 Design of pulse magnetized magnets
  • 7.7 Applications - Sensors
  • 7.8 Applications – Electrical machines
  • 7.9 Summary
  • Acknowledgments
  • References
  • Chapter 8 Hot formed NdFeB magnets
  • Abstract
  • 8.1 Introduction
  • 8.2 Development of hot-formed Nd-Fe-B magnets
  • 8.3 Characteristics of hot-deformed Nd-Fe-B magnets
  • 8.4 Fundamental research
  • 8.5 Applications
  • 8.6 Future outlook
  • 8.7 Concluding remarks
  • Acknowledgments
  • References
  • Chapter 09 Bonded Sm-Fe-N permanent magnets
  • Abstract
  • 9.1 Introduction
  • 9.2 Interstitial modification
  • 9.3 Basic characteristics of Sm-Fe-N compounds
  • 9.4 Magnet processing
  • 9.5 Applications
  • 9.6 Conclusion
  • Acknowledgments
  • References
  • Chapter 10 Critical materials for permanent magnets
  • Abstract
  • 10.1 Introduction
  • 10.2 What is a critical material?
  • 10.3 Critical materials in permanent magnets
  • 10.4 Effects of criticality on technology evolution, and vice versa
  • 10.5 Source diversification
  • 10.6 Substitution
  • 10.7 Summary
  • Acknowledgments
  • References
  • Chapter 11 Permanent magnet coatings and testing procedures
  • Abstract
  • 11.1 Introduction
  • 11.2 Magnet characteristics relevant to coating
  • 11.3 Coating permanent magnets
  • 11.4 Coating test and evaluation
  • 11.5 Summary
  • References
  • Glossary of Magnetic Terms
  • Index

Product details

  • No. of pages: 454
  • Language: English
  • Copyright: © Woodhead Publishing 2022
  • Published: January 27, 2022
  • Imprint: Woodhead Publishing
  • Paperback ISBN: 9780323886581
  • eBook ISBN: 9780323886406

About the Editors

John Croat

Dr. John J. Croat obtained a Ph.D. (1972) degree in Metallurgy from Iowa State University in 1972. Following graduation, he joined the Physics Department of the General Motors Research Laboratories, where he was involved primarily with the research and development of permanent magnet materials from rare earth-transition metal alloys. While there, he was instrumental in the discovery of rapidly solidified NdFeB magnetic powder and the development of bonded NdFeB magnets. He also played a key role in the development of the processes and equipment for manufacturing these materials. He received eleven patents in this area, including all of the US composition patents for NdFeB magnets. He has received a number of awards for this discovery including the 1885 Applications of Physics Prize awarded by the American Institute of Physics and the 1986 New Material Prize awarded by the American Physical Society. In 1994 he was the recipient of an Outstanding Engineering Achievement Award by the American Society of Metals. In 1984, he transferred to the Delco Remy Division of General Motors to help start the Magnequench business unit, which was formed to commercialize NdFeB magnets. Between 1984 and 1995 he held various positions at this company, including Chief Engineer, Sales Manager and, from 1991 to 1995, Managing Director of the business. In 1995, General Motors sold the Magnequench business to a group of international investors and he left the company. In 1997 Dr. Croat helped AMR Technologies create a new NdFeB magnetic powder business. This division was named Advanced Magnetic Materials (AMM) and produced rapidly solidified NdFeB magnetic powder at a manufacturing facility in Nakhonratchasima, Thailand. He served as President of this company until 2004 when AMR Technologies merged with Magnequench to form Neo Materials Technology. Since 2007 he has served as a consultant to the world-wide permanent magnet industry.

Affiliations and Expertise

Consultant, International Permanent Magnet Industry, Naples, Florida, USA

John Ormerod

Dr. John Ormerod obtained his PhD in Metallurgy from the University of Manchester in the United Kingdom in 1978. He has more than forty years of research, product development, and manufacturing experience in the area of metals, permanent magnets and magnetic materials. From 1979 to 1990 he worked for Phillips Electronics in the Netherlands and eventually became the General Manager of the rare earth magnet division. Between 1990 and 2002 he held the position of Vice President/General Manager of Arnold Engineering, a manufacturer of a wide range of permanent magnet materials located in Marengo, Illinois. In 2002 John was named President of Res Manufacturing in Milwaukee, Wisconsin. Res is a manufacturer of stamped metal components, assemblies and value added services to diversified industries. They are a major supplier of components and assemblies to Tesla Motors for their Model S and Model X electric vehicle platforms. In 2014 he founded JOC LLC, a consulting firm which provides a unique combination of business and technical expertise to the Global Magnetics and Metals Industries. Areas of expertise include technology assessment, IP analysis and patent review, industry analysis, operations management, strategic planning, budgeting, new product planning, acquisitions due diligence and sales and marketing consultations. Clients include IP law firms, major magnet manufacturers, magnetic equipment manufacturers, medical device R and D companies, motor manufacturers, tier 1 automotive suppliers and new magnetic material R and D businesses. John is currently a technical expert evaluating prior art for the Rare Earth Magnet Industry Alliance and has provided expert testimony at several USPTO patent trial proceedings related to various magnetic technologies. Most recently he provided expert testimony on issues of invalidity during the rare earth magnet ITC investigation of a number of Hitachi Magnetics patents on sintered Nd magnets.

Affiliations and Expertise

Consultant, International Permanent Magnet Industry, JOC LLC Consulting, Knoxville, TN, USA

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