Fused Perovskite Tunnel Structures in Ba5 Fe6+x S4+x O8 (0.44≤x≤0.55) with x-Dependent Two-Stage Magnetizations.

Ba5 Fe6+x S4+x O8 was synthesized through a solid-state reaction, and pure powders of nominal compositions x=0.44-0.55 were obtained after being rinsed with water. The crystal structures (P4/mmm, a=10.13, c=4.03 Å) and sample purities were investigated by powder synchrotron X-ray diffraction and were found to be composed of a tunnel lattice (Ba5 Fe6 S4 O8 ), built from fused perovskite units and the tunnel filling (Fex Sx ). The variable composition, that is, the tunnel filling (x), causes partially occupied sites as well as crystallographic split positions. Ba5 Fe6+x S4+x O8 (x=0.525) is semiconducting and all investigated compositions exhibit magnetic ground states that could be described as either semi-spin-glass-like (x>0.5) or canted antiferromagnetic (x<0.5). The spin-glass in x=0.525 exhibits magnetic relaxations that are affected by ageing.