Electron spin relaxation of N@C60 in CS2

• DOI: 10.1063/1.2147262
• Publication Date: 2006-01-04T23:12:43Z
• Authors: John J. L. Morton; Alexei M. Tyryshkin; Arzhang Ardavan; Kyriakos Porfyrakis; S. A. Lyon; G. Andrew D. Briggs
• Keywords: Condensed Matter - Materials Science; Materials Science (cond-mat.mtrl-sci); FOS: Physical sciences; 01 natural sciences; 0104 chemical sciences

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⩾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 0.25ms at 170K.