Coulomb spin liquid in anion-disordered pyrochlore Tb2Hf2O7

Abstract

The charge ordered structure of ions and vacancies characterizing rare-earth pyrochlore oxides serves as a model for the study of geometrically frustrated magnetism. The organization of magnetic ions into networks of corner-sharing tetrahedra gives rise to highly correlated magnetic phases with strong fluctuations, including spin liquids and spin ices. It is an open question how these ground states governed by local rules are affected by disorder. Here we demonstrate in the pyrochlore Tb2Hf2O7, that the vicinity of the disordering transition towards a defective fluorite structure translates into a tunable density of anion Frenkel disorder while cations remain ordered. Quenched random crystal fields and disordered exchange interactions can therefore be introduced into otherwise perfect pyrochlore lattices of magnetic ions. We show that disorder can play a crucial role in preventing long-range magnetic order at low temperatures, and instead induces a strongly fluctuating Coulomb spin liquid with defect-induced frozen magnetic degrees of freedom.

Disorder and Quantum Spin Ice

“…As it opens an original research route in the field of quantum spin ice and spin liquids, we hope that this work will arouse new theoretical developments taking especially into account the role of J ± . We also anticipate that experiments on other non-Kramers quantum spin ice candidates as Pr 2 Sn 2 O 7 [49], Pr 2 Hf 2 O 7 [50] and Tb 2 Hf 2 O 7 , where a strongly fluctuating Coulomb liquid phase coexists with defect induced frozen magnetic degrees of freedom [13], will be extremely interesting to test these ideas.…”

Frustrated Quantum Rare-Earth Pyrochlores

“…some manifestation of an extreme sensitivity to disorder. Studies of related compounds such as Tb 2 Sn 2 O 7 , which shows magnetic ordering into an ice state [118], or Tb 2 Hf 2 O 7 , which is thought to have strong structural disorder [119], may shed some light on these questions.…”

Magnetoelastic excitation spectrum in the rare-earth pyrochlore Tb2Ti2O7

“…8 each bear some resemblance to the structure factor of elastic scattering in various other model frustrated magnets. For E 1 the pronounced triangles pointing in toward (0, 0, 2) and, particularly, (2, 2, 0) resemble the pyrochlore Heisenberg antiferromagnet [88][89][90]; for E 2 the scattering is somewhat reminiscent of the pinch points and "butterflies" of intensity found in Tb 2 Ti 2 O 7 [37] or Tb 2 Hf 2 O 7 [91]; while for E 3 the scattering around the boundary of the first zone, at (0, 0, 3) and around the boundary of the (2, 2, 2) zone is somewhat similar to a dipolar spin ice [92] or a tiling of hexagonal clusters on the pyrochlore lattice [93,94].…”