title: Electron spin relaxation of N@C60 in CS2 in CS2.
abstract: We examine the temperature dependence of the electron spin relaxation times of the molecules N@C60 and N@C70 (which comprise atomic nitrogen trapped within a carbon cage) in liquid CS2 solution. The results are inconsistent with the fluctuating zero-field splitting (ZFS) mechanism, which is commonly invoked to explain electron spin relaxation for S> or =1 spins in liquid solution, and is the mechanism postulated in the literature for these systems. Instead, we find an Arrhenius temperature dependence for N@C60 , indicating the spin relaxation is driven primarily by an Orbach process. For the asymmetric N@C70 molecule, which has a permanent ZFS, we resolve an additional relaxation mechanism caused by the rapid reorientation of its ZFS. We also report the longest coherence time (T2) ever observed for a molecular electron spin, being 0.25 ms at 170 K.
authors.affiliation: Department of Materials, Oxford University, Oxford OX1 3PH, United Kingdom. john.morton@materials.ox.ac.uk
authors.forename: John J L
authors.initials: JJ
authors.lastname: Morton
authors.forename: Alexei M
authors.initials: AM
authors.lastname: Tyryshkin
authors.forename: Arzhang
authors.initials: A
authors.lastname: Ardavan
authors.forename: Kyriakos
authors.initials: K
authors.lastname: Porfyrakis
authors.forename: S A
authors.initials: SA
authors.lastname: Lyon
authors.forename: G
authors.initials: G
authors.lastname: Andrew D Briggs