1. General

1.1 The different types of permanent magnets

As mentioned in [D 2 101] , there are currently four main families of materials that account for the bulk of applications on the permanent magnet market.

These four families are, in order of appearance: Alnico, hard ferrites, samarium-cobalt and neodymium-iron-boron.

Alnico alloys based on aluminum, nickel, cobalt and iron first appeared in the 1930s. Today, they are used less and less, due to their modest magnetic properties and the high cost of cobalt. Thanks to their excellent thermal stability, they still have a few rare applications, in the high-temperature sector and on the measuring equipment market....