We examine the temperature dependence of the 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 > 1/2 spins in liquid solution, and is the mechanism postulated in the literature for these systems. Instead, we find a clear 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 non-zero 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 170K.
@article{arxiv.cond-mat/0510610,
title = {Electron spin relaxation of N@C60 in CS2},
author = {John J. L. Morton and Alexei M. Tyryshkin and Arzhang Ardavan and Kyriakos Porfyrakis and S. A. Lyon and G. Andrew D. Briggs},
journal= {arXiv preprint arXiv:cond-mat/0510610},
year = {2009}
}
Comments
6 pages, 6 figures V2: Updated to published version