Rare earth magnetic ordering in exchange-coupled superconductors

Abstract

Magnetic neutron diffraction measurements are reviewed for two families of superconductors where exchange interactions dominate the energetics of the magnetic system. One system is cuprates that contain Pr, which exhibit magnetic rare earth ordering temperatures that are an order-of-magnitude higher than for the other rare earths, and where f-electron hybridization effects destroy any chance for superconductivity. The second family of materials is the quaternary RNi2B2C borocarbides. These materials have comparable magnetic and superconducting transition temperatures, and exhibit a rich variety of commensurate and incommensurate magnetic structures that coexist and compete with the superconducting state.