Crystal-Field Symmetry Constraints in Layered Honeycomb ErBr 3
The study investigates how crystal-field symmetry restricts ErBr3's ground state to one of two classes. Thermodynamic measurements reveal two zero-field anomalies at 0.375 K and 0.200 K, linking this symmetry to the material's field-dependent response. Neutron scattering confirms the absence of low-energy magnetic modes, supporting a selection rule that suppresses lowest-order magnetic exchange processes.