  Spin angular momentum and mechanical rotation both contribute to the total
angular momentum of rigid bodies, leading to spin-rotational coupling via the
Einstein-de Haas and Barnett effects. Here we show that the revolutions of
symmetric nanorotors can be strongly affected by a small number of intrinsic
spins. The resulting dynamics are observable with freely rotating nanodiamonds
with embedded nitrogen-vacancy centers and persist for realistically-shaped
near-symmetric particles, opening the door to torque-free schemes to control
their rotations at the quantum level.
