Magnetic ordering and crystal nucleation in undercooled Co–based melts

Long–range magnetic order in metals and alloys is restricted to the solid state of matter, since the Curie temperatures of all known metallic materials are below their respective melting temperatures. This article reviews recent investigations on the maximum undercoolability of Co–based alloys, which show high relative Curie temperatures. Experiments on drops undercooled containerlessly by electromagnetic levitation show the onset of magnetic ordering when the temperature is approaching the Curie temperature. Studies of the nucleation behaviour propose a magnetic contribution to the activation energy to form crystal nuclei of critical size in deeply undercooled Co–rich melts.