Experimental signatures of phase competition in quantum XY pyrochlores

          @misc{ pirsa_PIRSA:17060036,
            doi = {10.48660/17060036},
            url = {https://pirsa.org/17060036},
            author = {Hallas, Alannah},
            keywords = {Condensed Matter},
            language = {en},
            title = {Experimental signatures of phase competition in  quantum XY pyrochlores},
            publisher = {Perimeter Institute},
            year = {2017},
            month = {jun},
            note = {PIRSA:17060036 see, \url{https://pirsa.org}}
          }
          

Abstract

The erbium and ytterbium rare earth pyrochlores exhibit local XY spin anisotropy. Experimental and theoretical investigations of XY pyrochlores have revealed a strong propensity for quantum magnetic phenomena, such as order-by-disorder and the quantum spin ice state. We have conducted a systematic investigation of the family of XY pyrochlores, Yb2B2O7 and Er2B2O7, spanning many non-magnetic B site cations (B = Ge, Ti, Pt, and Sn). We have characterized the magnetism of these XY pyrochlores using heat capacity, muon spin relaxation, neutron diffraction, and inelastic neutron scattering. A diversity of magnetic ground states and behaviours are represented among this family, ordered states ranging from ferromagnetic to antiferromagnetic, and in the case of one material, an absence of magnetic order to at least 100 mK. Moreover, we find that the magnetic ground state properties of these materials are strongly influenced by proximity to competing magnetic phases, consistent with theoretical predictions. We empirically demonstrate the signatures for phase competition in the frustrated XY pyrochlores: multiple heat capacity anomalies, suppressed TN or Tc, sample and pressure dependent ground states, and unconventional spin dynamics.