Vacuum fluctuations and the spin current in mesoscopic structures with collinear magnetic order

We show that in magnetic nanostructures with a homogeneous magnetic order, the equilibrium spin current can be nonzero. For example, this is the case of a wide magnetic ring with the magnetization along the ring axis. The physical reason of this effect is a variation of the orientation of anisotropy axis inducing a spin torque acting on the magnetic ions. The mechanism of the spin current generation is related to the quantum vacuum fluctuations in the magnetic system.