Abstract

The competition between superconductivity and antiferromagnetism has been a topic of much interest recently mainly as the result of the discovery of high-temperature superconductivity in the two dimensional cuprates and unusually high transition temperatures in the heavy fermion CeTIn5 system (where T=Co, Rh, or Ir). In the cuprates, superconductivity results by doping an insulating two-dimensional antiferromagnet with either holes or electrons.

In contrast, in the two dimensional CeTIn5 system, superconductivity emerges from a metallic spin-density wave ground state. I will present an experimental overview of the magnetic properties in the CeCoIn5 and YBa2Cu3O6+x superconductors. I will first provide an outline of YBa2Cu3O6+x illustrating how the magnetic properties (probed through the use of neutron scattering) evolve on doping the insulating phase to achieve high temperature superconductivity. This review will highlight some of the conflicting ideas describing this transition as well as some theoretical challenges. I will then provide a summary of the magnetic properties of superconducting CeCoIn5 and antiferromagnetic CeRhIn5. The results will be compared with current band calculations and experimental data for the cuprates. The nature of the critical point defining the transition to a superconductor in both systems will be discussed.