Coulomb-promoted spintromechanics in magnetic shuttle devices

Exchange forces on the movable dot ("shuttle") in a magnetic shuttle device depend on the parity of the number of shuttling electrons. The performance of such a device can therefore be tuned by changing the strength $U$ of Coulomb correlations to block or unblock parity fluctuations. We show that by increasing $U$ the spintro-mechanics of the device crosses over, at $U=U_c(T)$, from a mechanically stable regime to a regime of spin-induced shuttle instabilities. This is due to enhanced spin-dependent mechanical forces as parity fluctuations are reduced by a Coulomb blockade of tunneling and demonstrates that single-electron manipulation of single-spin controlled nano-mechanics is possible.