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Design Considerations

Because Alnico is hard and brittle and not suitable for drilling, tapping or conventional machining operations, it is not usually used as a structural component in product design.  We recommend selecting simple shapes when possible, fitting into slots rather than holes. Cross sections of less than .125" (3.18 mm) should be avoided.  Finishing increases cost, so if your application can use “as cast” or “as sintered” then cost will be lower.

For holding applications requiring mounting, or to protect the magnet, alnico assemblies such as rotors or magnetron magnets may be supplied with aluminum housings. Alnico may be painted for aesthetic reasons, like the ever popular red horseshoe magnet.

Demagnetization Curves

A second quadrant demagnetization curve provides information about the magnetic characteristics of a magnet, including the magnetic field strength and how resistant it is to demagnetize. How it is used in a magnetic circuit will affect its performance. When a permanent magnet is fully magnetized, its magnetic domains are aligned. Certain conditions such as temperature and reverse magnetic fields can cause some of the domains to lose this alignment and reverse, triggering the magnet to lose some or all of its magnetic field.

Resources

Adams 2016 Hard Magnet Materials Catalog
(7MB) Featuring a magnet materials overview, chart of materials properties and demagnetization curves for Neodymium, Samarium Cobalt, Ceramic (Ferrite) and Alnico materials offered by Adams.
Chart of Material Properties
Displays each permanent magnet material along with its Maximum Energy Product: Bhmax, Residual Flux Density: Br Gauss, Coercive Force: Hc Oersteds, Intrinsic Coercive Force: Hci Oersteds and Maximum Operating Temperature: C / F.
Breakaway Force of a Magnet
Explains the test methods used to determine how much force it takes to pull a magnet directly away from the surface it is attached to.
Standard Specifications for Permanent Magnet Materials
Defines thermal and mechanical characteristics and properties of commercially available permanent magnet materials including Alnico, Ceramic, Rare Earth (Samarium cobalt and neodymium) and Iron-Chromium-Cobalt. Includes a Glossary of Terms and Magnetic Quantities (Symbols, Units and Conversion Factors).