Tunneling, remanence, and frustration in dysprosium-based endohedral single-molecule magnets

Paramagnetic atoms inside nanometer sized fullerenes realize robust, and chemically protected, spin systems. Changing the stoichiometry of the endohedral clusters results in a variety of magnetic ground states, as it is demonstrated for ${\mathrm{Dy}}_{n}{\mathrm{Sc}}_{3\ensuremath{-}n}\mathrm{N@}{\mathrm{C}}_{80}$ ($n=1,2,3$). All three exhibit distinct hysteresis and qualify as single-molecule magnets. In zero field the magnetization of $n=1$ decays via quantum tunneling, while ferromagnetic coupling of the individual dysprosium moments results in remanence for ${\mathrm{Dy}}_{2}\mathrm{ScN@}{\mathrm{C}}_{80}$ and in a frustrated ground state for $n=3$. The latter ground state turns out to be one of the simplest realizations of a frustrated, ferromagnetically coupled, system.