Intrinsic Impurity-Band Stoner Ferromagnetism in C60Hn

We identify Stoner ferromagnetism in fcc C60Hn (n = odd) by using a local density approximation in the framework of the density functional theory. Hydrogen chemisorption on fullerenes creates quasi-localized pi electrons on the fullerene surface, overlapping of their wave functions giving rise to a narrow half filled impurity band in the fcc C60Hn. The Stoner-type ferromagnetic exchange between the itinerant electrons leads to spin-split impurity bands. The magnetic moment per C60Hn molecule is 1 mu(B) (for n = odd) or 0 (for n = even, including zero), only one of the hydrogens contributing to the spin-split states. Direct overlapping of the quasilocalized pi-electron orbitals is essential for the ferromagnetism.