Modeling stacking faults in the layered molecular-based magnets AM(II)Fe(C2O4)(3) {M-II = Mn, Fe; A = organic cation}

The influence of stacking faults in the crystal structures of molecular-bas ed magnets N(n-CnH2n+1)(4)(MFe)-Fe-II'(III)(C2O4)(3) {M-II Mn, Fe; n=3-5} i s discussed on the basis of X-ray powder diffraction profiles, Polycrystall ine samples of N(n-C5H11)(4) compounds are monophasic with orthorhombic uni t cells very similar to those of N(n-C5H11)(4)(MnFeIII)-Fe-II(C2O4)(3) dete rmined by single crystal data, However, polycrystalline N(n-C3H7)(4) and N( n-C4H9)(4) compounds are biphasic, containing varying contributions from R3 c and P6(3) phases, Structures containing stacking faults were modeled by a ssuming random interchange between R3c and P6(3) stacking within the crysta llites. X-ray diffraction profiles calculated from the model structures exh ibit broadening similar to that seen in the experimental profiles, The pres ence of stacking faults explains the difficulty in obtaining macroscopic si ngle crystals of the N(n-C3H7)(4) and N(n-C4H9)(4) compounds. (C) 1999 Acad emic Press.