Triangular Lattice of Ho³⁺ with S_eff = 1/2 in Antiferromagnetic KHoSe₂

The interactions among magnetic ions exhibit a significant dependence on their geometric arrangements within crystalline lattices. In the research presented herein, we detail the synthesis, structural elucidation, and examination of the magnetic properties of a novel compound, KHoSe₂. This compound is synthesized by utilizing the KCl salt flux technique. Through both X-ray and neutron powder diffraction analyses, we determine that KHoSe₂ adopts a trigonal crystal structure within the R3̅m space group (S.G.166), featuring a layered architecture. Within this structure, Ho³⁺ ions are arranged in a triangular lattice. Magnetic susceptibility measurements conducted down to T = 1.8 K reveal no evidence of long-range magnetic order. Additionally, neutron powder diffraction studies across various temperatures corroborate the absence of long-range magnetic ordering at temperatures exceeding 10 K. An anomalous feature in the specific heat capacity near T = 3.5 K, which has not been observed in other materials in this family, is observed. Furthermore, the specific heat capacity investigations also suggest an effective spin (S_eff) of 1/2 for KHoSe₂, which deviates from the anticipated value for an isolated Ho³⁺ ion.