Silver route to cuprate analogs

The parent compound of high- T c superconducting cuprates is a unique Mott insulator consisting of layers of spin- 1 2 ions forming a square lattice and with a record high in-plane antiferromagnetic coupling. Compounds with similar characteristics have long been searched for without success. Here, we use a combination of experimental and theoretical tools to show that commercial A g F 2 is an excellent cuprate analog with remarkably similar electronic parameters to L a 2 C u O 4 but larger buckling of planes. Two-magnon Raman scattering and inelastic neutron scattering reveal a superexchange constant reaching 70% of that of a typical cuprate. We argue that structures that reduce or eliminate the buckling of the A g F 2 planes could have an antiferromagnetic coupling that matches or surpasses the cuprates.