NdFeB

NdFeB magnets, or neodymium magnets, are a class of rare-earth permanent magnets composed primarily of neodymium, iron, and boron (Nd2Fe14B). They are the strongest commercially available magnets, offering very high energy density in compact sizes and enabling powerful magnetic performance in small form factors.

Composition and properties: The Nd2Fe14B phase provides a high maximum energy product (BHmax) typically in the 30–52 MGOe range for standard grades. They are temperature sensitive; coercivity and remanence fall as temperature rises. To improve high‑temperature performance, small amounts of dysprosium or terbium are often added, and some grades substitute praseodymium. They are brittle and require protective coatings to resist corrosion.

Manufacturing: Most NdFeB magnets are produced by powder metallurgy. The alloy is melted, atomized into powder, pressed with an aligning magnetic field, sintered, and heat-treated to optimize microstructure, then machined to final shapes. Finishing usually includes a protective coating such as nickel-copper-nickel or epoxy. Bonded NdFeB magnets, made by combining magnet powder with a polymer binder, offer better machinability and shock resistance but lower magnetic performance.

Types and shapes: Two main families exist—sintered NdFeB (higher energy, stronger) and bonded NdFeB (more ductile). Magnets are manufactured in various shapes, including discs, rings, blocks, and complex geometries, and can be magnetized in a single direction or multiple directions as required.

Applications: NdFeB magnets are widely used in electric motors (consumer electronics, robotics, automotive, wind turbines), generators, hard disk drives (historically), loudspeakers, and MRI equipment, among other devices that require strong permanent magnets in compact packages.

History and safety: They were developed in the early 1980s by Sumitomo Special Metals and General Motors and entered commercial use mid‑1980s. NdFeB magnets are brittle and prone to corrosion without coatings; they can pose safety risks if mishandled and raise environmental considerations in mining and recycling.