Anisotropic Alnico was introduced in 1940 and significant quantities were delivered in that decade. In 1957, 25% of the Cobalt used in the US went into Alnico magnets. They are composed of Aluminum, Nickel, Cobalt, a little Copper, and a lot of Iron.  

The highest energy Alnicos are cast; typically in sand molds, shell molds, or straws. Alloys can also be crushed into powder then cold pressed and sintered. Raw materials, cooling methods, and heat treatment programs are varied to optimize the induction, coercivity, and energy product necessary to satisfy the different customers’ needs. Most grades are also available unoriented.

These materials exhibit high induction, great resistance to corrosion, very low temperature coefficients, work at very high temperatures, and are easy to magnetize. They are used where very large temperature extremes exist and/or very stable magnetic and physical properties are required. But they have a low resistance to demagnetization, high Cobalt content, and the cast materials require extensive grinding. 

Alnico materials are relatively unique and satisfy requirements that few others can. Motors use them to provide a soft start without need for a controller and to provide temperature-stable performance. Sensors, relays, and traveling wave tubes use them because of their very small variability with temperature. They are used extensively in watt-hour meters & moving-magnet meters due to their ease of calibration and their long-term stability in changing environments. Alnico-containing microphones are often preferred because they provide the continuously rich sound for musicians. They are also the preferred material in guitar pickups because they provide the mellow tones that other magnetic materials cannot. 

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