Figure 1. Structures of the molecular magnetic helices and experimental set-up.

View of the simplified structure of the [M-NIT]_∞ molecular helices containing Co^II (a) and Mn^II(b) ions bridged by organic nitronyl-nitroxide radicals, with a radical unit highlighted by the red circle. The metal ions are highlighted as large spheres. The ancillary hfac ligands and the radical backbone are in grey, while the conjugated bonds carrying the magnetic exchange interaction are highlighted in yellow, with the radical oxygen atoms in red and nitrogen ones in blue. Some group of atoms, i.e. CF₃, CH₃, and O-CH₃, have been omitted for the sake of clarity. The helices develop along the crystallographic c axis of the P3₁/P3₂ space groups. The green arrows represent the orientation of the magnetic moments when the magnetic field is applied parallel to the c axis, which are not collinear to the field in the case of the anisotropic Co^II ions. c) Schematic side view of the geometry of the experiment where needle-like single crystals were mounted on a copper sample holder to form an angle of 15° between the chain direction and the propagation vector, $\overrightarrow{k}$, of the X-rays, which is parallel to the applied magnetic field. d) Photography of the sample mounting viewed from the top, with a ruler for reference.