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Electron spin relaxation of N@C60 in CS2

John J. L. Morton·Alexei M. Tyryshkin·Arzhang Ardavan·Kyriakos Porfyrakis·S. A. Lyon·G. Andrew D. Briggs
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Abstract

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.

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John J. L. Morton, Alexei M. Tyryshkin, Arzhang Ardavan, Kyriakos Porfyrakis, S. A. Lyon, G. Andrew D. Briggs. 2006-01-05. Electron spin relaxation of N@C60 in CS2. https://doi.org/10.1063/1.2147262

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