The main objective of this proposal is the magnetic structure characterization in function of the temperature below TN approx. 36 K. Below TN, the magnetic order in these compounds vary from a antiferromagnetic behaviour with a weak spin canting for [NH2(CH3)2]n[FeIIIMnII(HCOO)6]n compound to a ferromagnetic behavior for [NH2(CH3)2]n[FeIIICoII(HCOO)6]n compound. That is due to the different ions sublattices which are in competion (the different spin state involved in those complexes are S = 5/2, for Fe(III) and Mn(II) and 3/2 for Co(II), respectively). To elucidate the different magnetic behavior present in this compound, neutron diffraction techniques are mandatory.