Octahedral Lattice Distortion-Driven Ferroelectricity and Canted Antiferromagnetism in Oxalate and Phenanthrolin Ligand-Based Chain Molecular Magnets [{Fe(Δ)Fe(Δ)}1-x{Cr(Δ)Cr(Δ)}x(ox)2(phen)2}n(x=0, 0.1, and 0.5)

The hydrothermally synthesized chain molecular magnets [{Fe(Delta)Fe(Delta)}(1-x){Cr(Delta)Cr(Delta)}(x)(ox)(2)(phen)(2)](n)(x = 0, 0.1, and 0.5) were investigated using neutron diffraction. The structural analysis reveals that both the ox (oxalate) and phen (phenanthroline) ligands are connected to metal ions (M) of different symmetries {M-1(Delta) and M-2(Delta)}, forming an alternating zigzag chain-like structure with a single repeating unit of [phen-M-1(Delta)-ox-M-2(Delta)-phen](n). The neutron diffraction study at 2 K revealed that the magnetic structure of these compounds consists of two inequivalent Fe magnetic sublattices, each of which orders with a large component of magnetic moment along the a-axis and small components along the b- and c-axes: Fe-1 [m(a) = 4.17(6) mu(B), m(b) = 0.8(1), and m(c) = -1.07(4) mu(B )and Fe-2 [m(a) = -3.87(6) mu(B), m(b) = 0.8(1), and m(c) = 1.07(4) mu(B)] for the x = 0 compound. A net moment of 0.3(1) mu(B )per formula unit along the a-axis appears for the x = 0 compound. The net moment increases with Cr2+ substitution. The observed electric polarization for all these compounds is quantitatively correlated in terms of the derived electric dipole moment, manifested because of the lattice distortions at two inequivalent metal atom sites.