Neutron polarisation analysis of the magnetic ordering of the quasi-two-dimensional honeycomb network d20-(P(C6D5)4) FeIIFeIII(C2O4)3

The crystal structure of AM(II)M(III)(oxalate)(3) class of materials, with M being a transition metal ion, shows an alternating order of the M-II and M-III magnetic ions on a honeycomb lattice. In (P(C6D5)(4))FeFe(ox)(3) no long-range magnetic order has been observed but instead a diffuse magnetic component is present below 35 It. XYZ neutron spin polarisation analysis has been used to separate the magnetic scattering from the nuclear-coherent and spin-incoherent contribution. The magnetic elastic as well as the quasi-elastic magnetic scattering profile can be obtained unambigiously. In (P(C6D5)(4))FeFe(ox)(3) no long-range magnetic order exists, due to the random anisotropy effects introduced by the different electronic configurations of the Fe2+ and Fe3+ ions. A comparison with the long-range magnetic ordering observed in (P(C6D5)(4))MnFe(ox)(3) is made. (C) 1999 Elsevier Science B.V. All rights reserved.