Invar behaviour in crystalline and amorphous alloys

A review is given of the wide range of ferromagnetic materials which exhibit Invar characteristics. It is proposed to illustrate the thesis that Invar behaviour is very general among such materials and does not necessarily demand the following conditions to be satisfied: (1) presence of iron; (2) incipient antiferromagnetism; (3) heterogeneous alloying; (4) closeness to a martensite transformation.

For most but not all of the materials discussed weak itinerant ferromagnetism accompanies and causes Invar characteristics. An example counter to this behaviour is Fe₃Pt. Here, Pettifor and Roy proposed as the origin of Invar behaviour a more general itinerant electron instability than is characteristic of weak itinerancy.