What’s the difference between Alnico, Sm-Co & Nd-Fe-B magnet materials?

Alnico is an older magnet material that still has important applications. Its maximum energy product is about 1/5 of Sm-Co materials, but it has excellent elevated temperature properties and has better corrosion resistance.

Alnico can be cast into different shapes with various magnetic orientations. The rare earth Sm-Co and NdFeB magnets have high coercivity, so they do not need to be magnetized in circuit and can be used with low permeance coefficients (i.e. thin discs).

These materials also lend themselves to Helmholtz coil testing due to their straight line normal curves. This also makes rare earths ideal for SMC and high field dipoles. Sm-Co has a good resistance to thermal demagnetization but is brittle.

NdFeB is less brittle, has poor thermal properties, and is prone to corrosion.