Abstract
The recent discoveries of proximate quantum spin-liquid compounds and their potential application in quantum computing informs the search for new candidate materials for quantum spin-ice and spin-liquid physics. While the majority of such work has centered on members of the pyrochlore family due to their inherently frustrated linked tetrahedral structure, the rare-earth pyrogermanates also show promise for possible frustrated magnetic behavior. With the familiar stoichiometry R2Ge2O7, these compounds generally have tetragonal symmetry with a rare-earth sublattice built of a spiral of alternating edge and corner-sharing rare-earth site triangles. Studies on Dy2Ge2O7 and Ho2Ge2O7 have shown tunable low temperature antiferromagnetic order, a high frustration index, and spin-ice-like dynamics. Here we use neutron diffraction to study magnetic order in Er2Ge2O7 (space group P41212) and find the lowest yet Neél temperature in the pyrogermanates of 1.15 K. Using neutron powder diffraction, we find the magnetic structure to order with k=(0,0,0) ordering vector, magnetic space group symmetry P4′1212′, and a refined Er moment of m=8.1μB near the expected value for the Er3+ free ion. Provocatively, the magnetic structure exhibits similar “local Ising” behavior to that seen in the pyrocholres where the Er moment points up or down along the short Er-Er bond. Upon applying a magnetic field, we find a first-order metamagnetic transition at ∼0.35T to a lower symmetry P2′12′12 structure. This magnetic transition involves an inversion of Er moments aligned antiparallel to the applied field describing a class I spin-flip-type transition, indicating a strong local anisotropy at the Er site—reminiscent of that seen in the spin-ice pyrochlores.
