The properties of materials are mostly evidenced and well characterized via investigations versus external effects of temperature, pressure, electrical or magnetic fields, irradiation or various mechanical tensions. An evidence of a canting arrangement of magnetic moments (expected by the angle between two planes locating iron in Fe-phthalocyanine) was possible only when an external field was applied. In the same compound, it was observed an unexpected increased orbital contribution with higher applied fields to the effective field at nucleus, over passing the algebraic sum of the internal and applied fields, together with the evidence of a non frozen orbital moment. The oxalate containing multiple-valence ions exhibited anti-ferromagnetic couplings both intra and inter molecular (rarely appearing simultaneously) what were well attested in fields of 8 Tesla. In the tetra-nuclear Fe3Ln molecular compounds the ordering was promoted by applied fields, what also helped in defining the spin structure of the molecules. Depending on the rare earth ion (Ln) it could be distinguished various behaviors with increasing applied field for the three sub-lattices of Fe3+ ions. The presence of external magnetic fields provided demonstration of an antiferromagnetic arrangement of spins in Fe7- wheel type- molecule pointing that the resulting molecular spin (S=5/2) derived from the one Fe located on central position of the structure. The observed magnetic relaxation, at 3 K, was not completely reduced even in fields up to 6 T, as deduced from comparison of the line widths to those of spectra at room temperature. Very high fields (8, 10, 14 T) were necessary to produce magnetic ordering in Fe(NO3)3 as well as a spiral rotations around c-axis of the three consecutive iron containing planes of the molecule.