Pyrochlores across the Metal-Insulator transition

Systems based on a triangular or pyrochlore lattice of corner sharing tetrahedra with nearest neighbor antiferromagnetic exchange interactions are the archetypal examples of geometric magnetic frustration, offering a means of accessing novel ground states. Magnetic systems based on 4d and 5d transition metal ions on the pyrochlore lattice offer a unique opportunity to explore the exotic ground states which potentially arise when the electron-electron Coulomb interaction, electronic bandwidth and spin orbit coupling are all of comparable magnitude. I will describe magnetization and muon spin relaxation investigations of a series of 4d Ru4+ based pyrochlores, which may be controllably tuned through a metal insulator transition, providing insight into the magnetic correlations as these finely balanced systems evolve from a localized to itinerant spin character.