Synthesis, Structure, and Magnetic Properties of Cyanurates RE₅(C₃N₃O₃)(OH)₁₂ (RE = Gd–Lu): Cryogenic Magnetocaloric Candidate Gd₅(C₃N₃O₃)(OH)₁₂

Rare-earth (RE)-based frustrated magnets are fertile playgrounds for discovering exotic quantum phenomena and exploring adiabatic demagnetization refrigeration applications. Here, we report the synthesis, structure, and magnetic properties of a family of rare-earth cyanurates RE₅(C₃N₃O₃)(OH)₁₂ (RE = Gd–Lu) with an acentric space group P6̅2m. Magnetic susceptibility χ(T) and isothermal magnetization M(H) measurements manifest that RE₅(C₃N₃O₃)(OH)₁₂ (RE = Gd, Dy–Yb) compounds exhibit no magnetic ordering down to 2 K, while Tb₅(C₃N₃O₃)(OH)₁₂ shows long-range magnetic ordering around 3.6 K. Among them, magnetically frustrated spin-⁷/₂ Gd₅(C₃N₃O₃)(OH)₁₂ shows long-range magnetic ordering around 1.25 K and a large magnetocaloric effect with a maximum magnetic entropy change ΔS_m of up to 58.1 J kg^–1 K^–1 at ΔH = 7 T at liquid-helium temperature regimes.