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A method for studying the magnetic dynamics of endofullerenes M@C2n (2n = 60, 70, …) and their derivatives, including fullerenols M@C2n(OH)X (X ~ 30) encapsulating 4 f elements inside carbon cages is studied. The possibilities of the 3D polarimetry of thermal, cold, and very cold neutrons for analyzing magnetic modes in organometallic systems and, in particular, in ensembles of endofullerenes, are discussed. Use of the spin dependence of coherent and incoherent neutron scattering at the nuclear and magnetic subsystems of samples is proposed. The dipole interactions of such objects are significant in solutions and colloidal systems, where they create molecular aggregates with complex magnetic dynamics, including soft relaxation modes. Their study using very-low-energy neutrons is important for an understanding of self-organization mechanisms and the biomedical applications of endofullerenes.

Concept of spin echo spectrometer on very cold neutrons (wavelengths λ ~ 10‒30 nm) to provide extra high resolution in energy transfer (ΔE ~ 10–13 eV) has been proposed. Simultaneous measurements of spin echo signals at different wavelengths will be realized using broadband spin flippers in combination with Fourier-analysis of λ-spectrum. The application of very cold neutrons should extend the spin echo time diapason radically, t ~ 10–12‒10–3 s. This promises to open a set of novel scientific areas including the spectroscopy of chemical reactions and catalytic processes, conformational transitions in polymers and biological molecules, dynamic modes in carbon structures (fullerenes, nanotubes, graphenes) at scales from few nanometers to microns. Presently, the development of NSE-spectrometer on VCN becomes relevant since the project of ultra cold neutron source at WWR-M reactor (PNPI) is in progress.