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Strain Effect on the Ultrafast Spin Switching of Cobalt-Doped Carbon Fullerenes

Endohedral fullerenes can realize robust and chemically protected spin systems, and are the promising candidates for molecular spintronics owing to their long magnetic relaxation times. In this paper, we take one- and two-magnetic-center Co-doped carbon fullerenes, specifically [Co<sub>2</sub>@C<sub>60</sub>]<sup>+</sup> and Co<sub>2</sub>@C<sub>60</sub>, as examples to study their ultrafast, laser-induced, spin dynamics through ab initio calculations. In particular, the strain modulation on the spin-switching process is investigated in detail. It is shown that the local spin switching on the Co atom of the molecular ion [Co<sub>2</sub>@C<sub>60</sub>]<sup>+</sup> and the simultaneous spin switching on both the Co atoms of the neutral system Co<sub>2</sub>@C<sub>60</sub> can be accomplished via Λ processes on the subpicosecond time scale. It is interesting that the spin-switching process on the endohedral fullerene Co<sub>2</sub>@C<sub>60</sub> can be speeded up when the system is subjected to an increasing tensile strain. It is demonstrated that the achieved various spin-switching scenarios result from the combination of the applied strain and the configuration of the system. The present results reveal the great potential of using magnetic endohedral fullerenes for active spin control and hence functionalization in the future spintronic devices.