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

The influence of stacking faults in the crystal structures of molecular-based magnets N(n-CnH2n+1)(4)(MFe)-Fe-II'(III)(C2O4)(3) {M-II Mn, Fe; n=3-5} is discussed on the basis of X-ray powder diffraction profiles, Polycrystalline samples of N(n-C5H11)(4) compounds are monophasic with orthorhombic unit cells very similar to those of N(n-C5H11)(4)(MnFeIII)-Fe-II(C2O4)(3) determined by single crystal data, However, polycrystalline N(n-C3H7)(4) and N(n-C4H9)(4) compounds are biphasic, containing varying contributions from R3c and P6(3) phases, Structures containing stacking faults were modeled by assuming random interchange between R3c and P6(3) stacking within the crystallites. X-ray diffraction profiles calculated from the model structures exhibit broadening similar to that seen in the experimental profiles, The presence of stacking faults explains the difficulty in obtaining macroscopic single crystals of the N(n-C3H7)(4) and N(n-C4H9)(4) compounds. (C) 1999 Academic Press.