Cooperative Jahn–Teller distortion leading to the spin-1/2 uniform antiferromagnetic chains in triclinic perovskites AgCuF3 and NaCuF3

Polycrystalline samples of AgCuF3, isostructural with NaCuF3, were synthesized by solid state reaction and characterized by powder X-ray diffraction. The magnetic properties of AgCuF3 and NaCuF3 were examined by measuring their magnetic susceptibilities and evaluating their spin exchange interactions. The three-dimensional CuF3 network of corner-sharing CuF6 octahedra present in AgCuF3 and NaCuF3 shows a cooperative Jahn–Teller distortion such that their magnetic susceptibilities above 50 K are well described by an S = 1/2 Heisenberg uniform antiferromagnetic chain model with average spin exchange of J/kB ≈ −300 and −180 K, respectively. The relative strengths of these interactions are well reproduced by spin dimer analysis based on tight-binding calculations, but not by mapping analysis based on first principles density functional calculations.

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