  We report our theoretical study on nucleation of a magnetic vortex around a
nonmagnetic impurity doped into ferromagnets. The mechanism lies in the
asymmetric Dzyaloshinskii-Moriya interaction arising from the breaking of
spatial inversion symmetry by the impurity. By using the spin-wave analysis and
Monte Carlo simulations, we show that the asymmetric interaction induces a
magnetic vortex with nonzero vorticity $l=+1$. The vortex is stabilized even
for less frustration in exchange interactions and in the absence of an external
magnetic field. We also find that the magnetic vortex is characterized by
magnetic multipoles according to its vorticity and helicity. We demonstrate a
potential realization of such a magnetic vortex by considering a monolayer
ferromagnet on a nonmagnetic substrate, which results in the magnetic monopole
and toroidal dipole.
