Investigating the origin of zero moment layers in triangular lattice K₃Er(VO₄)₂

Spin-1/2 antiferromagnetic triangular lattice systems are paradigms of geometrical frustration, exhibiting diverse ground states depending on exchange anisotropy and crystal-field effects. The rare-earth double vanadate glaserite K₃Er(VO₄)₂ is a quasi-two-dimensional isosceles triangular antiferromagnet that orders below 0.15 K into a unique structure of antiferromagnetically aligned b-axis moments alternating with layers of zero net moment. The vanishing moment has been proposed to be attributed to suppression of the out-of-plane pseudospin arising from strong XY single-ion anisotropy. To elucidate the origin of these zero-moment layers, we have performed half-polarized neutron diffraction, diffuse neutron scattering, and crystal electric field measurements. The half-polarized results indicate that the magnetic susceptibility tensor is largely confined to the ab plane but permits a small c-axis component. Preliminary diffuse scattering analysis suggests the zero-moment layers are magnetically disordered, revealing a more complex ground state.