Anisotropic magnetism on the square-lattice, the case of Dy-based oxyhalides

Rare-earth ions often display anisotropic magnetization distributions and are enticing in searching for exotic forms of magnetic matter. We present an investigation into the magnetic properties of a series of three Dysprosium-Oxyhalides (DyOX) compounds: DyOCl, DyOBr, and DyOI. These materials exhibit layered square lattices, with the primary difference between compounds being the inter-layer spacing, which is dependent on the size of the halide ion. This structure allows for a frustrated J₁-J₂ model with tunable off-diagonal exchange interactions due to spin-orbit on the ligands. Several forms of data have been analyzed, including x-ray diffraction, neutron scattering, and thermodynamic measurements such as heat capacity and magnetic susceptibility. Analysis of heat capacity reveals the presence of magnetic ordering below 7K with a secondary peak that occurs higher in temperature, which implies some additional ordering transition. We will discuss the origin of this peak and the unique magnetic behavior of these compounds.