Search for quantum phases in the rare earth zirconate and hafnate pyrochlore frustrated magnets

Pyrochlores are interesting due to their versatile structure, frustrated magnetic lattice and their wide variety of exotic magnetic ground states (spin ices, spin frozen states, or long-range ordered states). The most studied pyrochlore oxides are the classical spin ices Dy₂Ti₂O₇ and Ho₂Ti₂O₇. One of the most interesting avenues of current research is into systems which exhibit novel magnetic ground states, such as quantum spin liquid (QSL) and quantum spin ice (QSI). Pr, Tb or Yb pyrochlores are good candidates for the realisation of quantum states. We have studied the zirconate and hafnate R₂M₂O₇ (R= Rare Earth, M= Zr, Hf) oxides. Recent results show that they exhibit a variety of exciting magnetic behaviours and emergent properties, ranging from a disordered state with quadrupolar correlations and spin-ice-like excitations in Pr₂Zr₂O₇, the fragmentation of magnetic moments into an ordered phase and a fluctuating state in Nd₂Zr₂O₇, a disorder-induced QSL state in Tb₂Hf₂O₇, to a potential QSI ground state with fractionalized excitations in Pr₂Hf₂O₇. These investigations have been motivated by the availability of large high-quality single crystals of these materials. I will discuss the structural and magnetic characteristics of some of the zirconate and hafnate pyrochlores.