Doping of Bi4Fe5O13F with pentagonal Cairo lattice with Cr and Mn: Synthesis, structure and magnetic properties

Abstract The substitution of Cr 3+ and Mn 3+ for Fe 3+ in the Bi 4 Fe 5 O 13 F oxyfluoride featuring the magnetically frustrated pentagonal Cairo lattice is reported. Bi 4 Fe 4.1 Cr 0.9 O 13 F and Bi 4 Fe 4.2 Mn 0.8 O 13 F have been prepared using a solid state reaction in inert atmosphere. Their crystal structures were studied with transmission electron microscopy, powder X-ray diffraction and 57 Fe Mossbauer spectroscopy (S.G. P 4 2 / mbc , a  = 8.27836(2) A, c  = 18.00330(9) A, R F  = 0.031 (Bi 4 Fe 4.1 Cr 0.9 O 13 F), a  = 8.29535(3) A, c  = 18.0060(1) A, R F  = 0.027 (Bi 4 Fe 4.2 Mn 0.8 O 13 F)). The structures are formed by infinite rutile-like chains of the edge-sharing BO 6 octahedra (B—transition metal cations) linked by the Fe 2 O 7 groups of two corner-sharing tetrahedra. The voids in thus formed framework are occupied by the Bi 4 F tetrahedra. The 57 Fe Mossbauer spectroscopy reveals that Cr 3+ and Mn 3+ replace Fe 3+ exclusively at the octahedral positions. The Mn- and Cr-doped compounds demonstrate antiferromagnetic ordering below T N  = 165 K and 120 K, respectively.