The Elements of Magnetics
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The Elements of Magnetics Steve Constantinides Arnold Magnetic Technologies Corporation, 770 Linden Avenue, Rochester, NY 14625, U.S.A. ABSTRACT The 20th century saw rapid and dramatic improvements in permanent magnet materials. It has been 31 years since the discovery of neodymium-iron-boron and numerous companies and laboratories are seeking to produce a new and superior material. Topics discussed herein are material options, economics of selected materials and market drivers in material selection. Market issues include manufacturability by shape, size, and material yield; raw material supply including cost and dependability of the supply chain; raw material and magnet product price stability; development of applications based on commercial needs, government legislation and consumer demand. “Need is the mother of invention” and no discussion would be complete without covering why a new material would be beneficial from an applications point of view especially in energy production and consumption. Therefore, an introduction will be provided for select, major applications using permanent magnets and the growth forecasts for these. INTRODUCTION Research in magnetic materials has been conducted for a few hundred years. Permanent magnets have especially benefitted from advances in key magnetic properties. The 20th century saw particularly significant improvements. (1) The last substantially improved material has been so superior to any that came before that it has been widely adopted and not surpassed. This material is neodymium-iron-boron (NdFeB, “Neo”). It was discovered in 1981 by accident at the Naval Research Laboratories during research for an improved soft magnetic material. Three patents were issued for it including process, composition and product patents. The material was then optimized and commercialized by both Sumitomo and General Motors and numerous other companies in Europe, the USA and China. The first commercial magnets were sold by Crucible Magnetics of Elizabethtown, Kentucky, in November of 1984. The first major application for Neo was in hard disk drives. By 1990, it was estimated that 75% of Neo production was for the sintered magnets used to move the read/write head and for the compression bonded ring magnet in the spindle motor of hard disk drives. Other motors also benefitted from Neo magnets’ combination of high magnetic output and relatively low price. During the 1980s and early 1990s almost all the rare earths used in magnets came from Molycorp’s Mtn. Pass California mine. The mine was operated primarily for other rare earths such as europium for color cathode ray tubes and cerium for glass polishing. The magnet rare earths were sold from the residual materials after separation. By the mid 1990’s the demand for neodymium exceeded what was extracted in natural ratio causing stockpiling of cerium and lanthanum.(2) By the late 1990s China had become a major supplier of rare earths (oxides, metals and alloys) eroding Molycorp’s domination of the market.(3)
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By the great recession of 2009, a
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