Electron spin coherence in metallofullerenes: Y, Sc, and La@C₈₂

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 (T₂) 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 T₂ in deuterated o-terphenyl greater than 200  µs for Y, Sc, and La@C₈₂. The mechanisms governing relaxation (T₁, T₂) arise from metal-cage vibrational modes, spin-orbit coupling and the nuclear spin environment. The T₂ 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. ©2010 The American Physical Society