Strontium manganese selenite chloride Sr2Mn(SeO3)2Cl2: synthesis, crystal structure, optics, thermodynamics and first principles calculations

Newly synthesized strontium manganese selenite chloride, Sr₂Mn(SeO₃)₂Cl₂ extend Sr₂M(SeO₃)₂Cl₂ family, crystallizes in monoclinic space group P2₁/n (№14) with the unit cell parameters a = 5.45700(4) Å, b = 6.40651(5) Å, с = 12.56244(9) Å, β = 92.8829(4)°, Z = 2. Its crystal structure is comprised by dense layers of edge-sharing SrO₆Cl₂ polyhedra, which are separated by isolated chains of MnO₄Cl₂ octahedra interlinked by SeO₃ trigonal pyramids. In qualitative agreement with density functional theory calculations the title compound is an indirect wide-gap semiconductor with a gap Δ = 4.7 eV. Magnetically, it experiences consecutive short-range and long-range antiferromagnetic order. Below Neel temperature T_N = 3 K, Sr₂Mn(SeO₃)₂Cl₂ evidences a succession of spin-flop at μ₀H₁ = 1.79 T and spin-flip at μ₀H₂ = 5.67 T transitions. Intrachain J₁ = − 0.52 K and interchain J₂ = − 0.02 K exchange interactions differ by order of magnitude making the title compound a quasi-one-dimensional spin S = 5/2 system.