Structure and physical properties of 1D magnetic chalcogenide, jamesonite (FePb4Sb6S14)

Monoclinic FePb4Sb6S14 phase, jamesonite, which is a candidate material as a S = 2 Haldane compound, has been synthesized by the direct reaction of elements under dry conditions with sealed evacuated quartz tubes. The congruent melting point was determined at 592 degreesC by DTA measurements. Shiny metallic gray needle crystals grow on the surface of bulk heated at 550 degreesC. The elongated direction of each needle crystal is parallel to the c-axis. The crystal structure refinement (P2(1)/a, a = 15.750(6) Angstrom, b = 19.125(3) Angstrom, c = 4.030(4) Angstrom, beta = 91.68(8)degrees, V = 1213(1) Angstrom(3), Z = 2, D-c = 5.651 g/cm(3), R-1 = 3.16%) reveals the presence of two rod substructures elongated parallel to the c-axis. One is the lozenge-shaped Bi2Te3-type (or called SnS archetype), (3)(infinity)[Pb4Sb6S13]. The other is the novel single magnetic one-dimensional (1D) straight chain, (1)(infinity)[FeS6]. This compound shows intrinsic semiconductor behavior in the electric conductivity measurements. The optical band gap, 0.48 eV, is estimated by near-IR diffuse reflectance measurements. In the magnetic susceptibility measurements, this compound shows 1D-Heisenberg antiferromagnetic behavior with a broad peak at similar to33.5 K, where Fe2+ takes the high-spin state, t(2g)(4)e(g)(2). A possibility for the S = 2 Haldane system is discussed.