Endohedral fullerenes encapsulating a spin-active atom or ion within a carbon cage offer a route to self-assembled arrays such as spin chains. In the case of metallofullerenes the charge transfer between the atom and the fullerene cage has been thought to limit the electron spin phase coherence time $\left(T_2\right)$ to the order of a few microseconds. We study electron spin relaxation in several species of metallofullerene as a function of temperature and solvent environment, yielding a maximum $T_2$ in deuterated o-terphenyl greater than $200\mu \text{s}$ for Y, Sc, and ${\text{La@C}}_{82}$. The mechanisms governing relaxation ($T_1$, $T_2$) arise from metal-cage vibrational modes, spin-orbit coupling and the nuclear spin environment. The $T_2$ times are over 2 orders of magnitude longer than previously reported and consequently make metallofullerenes of interest in areas such as spin labeling, spintronics, and quantum computing.

• Received 9 June 2010

DOI:https://doi.org/10.1103/PhysRevB.82.033410