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The relatively low rare earth content (12% by volume, 26.7% by mass) and the relative abundance of neodymium and iron compared with samarium and cobalt makes neodymium magnets lower in price than samarium-cobalt magnets. The diamagnetic boron atoms do not contribute directly to the magnetism but improve cohesion by strong covalent bonding. The Nd 2Fe 14B crystal structure can be described as alternating layers of iron atoms and a neodymium-boron compound. In practice, the magnetic properties of neodymium magnets depend on the alloy composition, microstructure, and manufacturing technique employed. This magnetic energy property is higher in NdFeB alloys than in samarium cobalt (SmCo) magnets, which were the first type of rare-earth magnet to be commercialized. This magnetic energy value is about 18 times greater than "ordinary" ferrite magnets by volume and 12 times by mass. Therefore, as the maximum energy density is proportional to J s 2, this magnetic phase has the potential for storing large amounts of magnetic energy ( BH max ≈ 512 kJ/m 3 or 64 MG This gives the Nd 2Fe 14B compound a high saturation magnetization ( J s ≈ 1.6 T or 16 kG) and a remnant magnetization of typically 1.3 teslas. In a magnet it is the unpaired electrons, aligned so that their spin is in the same direction, which generate the magnetic field. The neodymium atom can have a large magnetic dipole moment because it has 4 unpaired electrons in its electron structure as opposed to (on average) 3 in iron. The resistance of the crystal lattice to turning its direction of magnetization gives the compound a very high coercivity, or resistance to being demagnetized. Like other magnets, the neodymium magnet alloy is composed of microcrystalline grains which are aligned in a powerful magnetic field during manufacture so their magnetic axes all point in the same direction. This means a crystal of the material preferentially magnetizes along a specific crystal axis but is very difficult to magnetize in other directions. Magnetic field strength H in units of A/m versus magnetic moment in A The most important is that the tetragonal Nd 2Fe 14B crystal structure has exceptionally high uniaxial magnetocrystalline anisotropy ( H A ≈ 7 T – The strength of neodymium magnets is the result of several factors. Neodymium magnets are made from compounds of neodymium with transition metals such as iron that are ferromagnetic, with Curie temperatures well above room temperature. In its pure form, neodymium has magnetic properties-specifically, it is antiferromagnetic-but only at temperatures, below 19 K (−254.2 ☌ −425.5 ☏).
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This perspective has been criticized for failing to recognize that most wind turbines do not use permanent magnets and for underestimating the power of economic incentives for expanded production. Because of its role in permanent magnets used for wind turbines, it has been argued that neodymium will be one of the main objects of geopolitical competition in a world running on renewable energy. In 2011, ARPA-E awarded 31.6 million dollars to fund Rare-Earth Substitute projects. The Advanced Research Projects Agency-Energy has sponsored a Rare Earth Alternatives in Critical Technologies (REACT) program, to develop alternative materials. The United States Department of Energy has identified a need to find substitutes for rare-earth metals in permanent magnet technology and has funded such research. Ĭhinese manufacturers have become a dominant force in neodymium magnet production, based on their control of much of the world's rare-earth mines. Hitachi has held more than 600 patents covering neodymium magnets. The Sumitomo facility became part of the Hitachi Corporation, and has manufactured but also licensed other companies to produce sintered Nd 2Fe 14B magnets. The company supplied melt-spun Nd 2Fe 14B powder to bonded magnet manufacturers. GM commercialized its inventions of isotropic Neo powder, bonded neo magnets, and the related production processes by founding Magnequench in 1986 (Magnequench has since become part of Neo Materials Technology, Inc., which later merged into Molycorp). GM focused on the development of melt-spun nanocrystalline Nd 2Fe 14B magnets, while Sumitomo developed full-density sintered Nd 2Fe 14B magnets. The research was initially driven by the high raw materials cost of SmCo permanent magnets, which had been developed earlier.
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General Motors (GM) and Sumitomo Special Metals independently discovered the Nd 2Fe 14B compound almost simultaneously in 1984.