Can magnetism and superconductivity coexist?

Abstract

Recent syntheses of rare earth (RE) ternary superconductors such as (RE)Mo₆X₈ (X = S or Se) and (RE)Rh₄B₄ have provided the first opportunity to explore the interaction between magnetism and superconductivity in detail owing to their particular crystal structure. The regular sublattice of the rare-earth ions in these new ternary compounds undergoes a ferro- or antiferromagnetic phase transition in the superconducting state. If the transition is antiferromagnetic, the superconductivity is preserved so that true coexistence results. If it is ferromagnetic, on the other hand, the superconductivity eventually gives way to uniform ferromagnetism at low temperatures. However, recent theories predict several possible states of coexistence even in ferromagnetic superconductors. This article reviews intriguing aspects of these new phase transitions in ternary superconductors.