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Evidence for SrHo2O4 and SrDy2O4 as model J1-J2 zig-zag chain materials

This presentation will focus on the Ho and Dy members of the recently discovered SrR2O4 family of frustrated rare-earth (R) materials. Despite the R sites forming a honey-comb in the ab plane, we will demonstrate that the physics is dominated by 1D correlations in the c-direction and that the magnetism in SrHoJ 1 -J 2 and SrDyJ 1 -J 2 can be mapped on to the Ising J 1 -J 2 spin chain model.

Three-dimensional magnetic order is suppressed from theta omega = -16.9 K to TN = 0.66 K in SrHoJ 1 -J 2 and is not observed to 50 mK in SrDy 2 O 4 . Our neutron powder diraction measurements indicate that prior to the 3D order in the SrHo 2 O 4 compound a 1D magnetically correlated state exists and that a similar state is found at the lowest measured temperatures in SrDy 2 O 4 . The correlation lengths of the 1D fluctuations have been extracted from neutron powder scattering data and, from ts to the 3D magnetic order found in the Ho analogue, the local correlations can be understood to have an up-up-down-down arrangement (""##) as expected in the ground state of a J 1 -J 2 spin chain model. The local Ising anisotropy was determined with an electrostatic point charge model that was used to fit crystal field excitations found with inelastic neutron scattering measurements. The combination of the strong local anisotropy and the low dimensional scattering strongly
suggest that these materials are realisations of the Ising J 1 -J 2 spin chain model at the classical limit.