Synthesis, crystal structure, and magnetic order of the layered iron oxycarbonate Sr4Fe2O6CO3

The iron oxycarbonate Sr4Fe2O6CO3 is reported. The crystal structure and ma gnetic order were determined by magnetic susceptibility, powder neutron dif fraction, and neutron scattering studies. The structure is tetragonal betwe en 10 and 400 K (I4/mmm, a = 3.88907(4) Angstrom and c = 27.9818(4) Angstro m at 295 K), and is related to a 4:3 type Ruddlesden-Popper phase with CO3 plaques in place of the middle layer of transition metal octahedra. The thr ee-dimensional magnetic ordering transition temperature is 361 K, The magne tic order is antiferromagnetic within the FeO2/SrO/SrO/FeO2 blocks and ferr omagnetic between blocks. (C) 2000 Academic Press.