  The physical characterisation and understanding of molecular magnetic
materials is one of the most important steps towards the integration of such
systems in hybrid spintronic devices. Amongst the many characterisation
techniques employed in such a task, Inelastic Neutron Scattering (INS) stands
as one of the most powerful and sensitive tools to investigate their spin
dynamics. Herein, the magnetic properties and spin dynamics of two dinuclear
complexes, namely [(M(hfacac)$_2$)$_2$(bpym)] (where M = Ni$^{2+}$, Co$^{2+}$,
abbreviated in the following as Ni$_2$, Co$_2$) are reported. These are model
systems that could constitute fundamental units of future spintronic devices.
By exploiting the highly sensitive IN5 Cold INS spectrometer, we are able to
gain a deep insight into the spin dynamics of Ni$_2$ and to fully obtain the
microscopic spin Hamiltonian parameters; while for Co$_2$, a multitude of INS
transitions are observed demonstrating the complexity of the magnetic
properties of octahedral cobalt-based systems.
