  We investigate the phase ordering kinetics of skyrmion lattice (SkL) in a
metallic magnet. The SkL can be viewed as a superposition of magnetic stripes
whose periods are determined by the quasi-nesting wave vectors of the
underlying Fermi surface. An effective magnetic Hamiltonian that describes the
electron-mediated spin-spin interaction is obtained for a two-dimensional s-d
model with the Rashba spin-orbit coupling. Large-scale Landau-Lifshitz-Gilbert
dynamics simulations based on the effective spin Hamiltonian reveal a two-stage
phase ordering of the SkL phase after a thermal quench. The initial fast
crystallization of skyrmions is followed by a slow relaxation dominated by the
annihilation dynamics of dislocations, which are topological defects of the
constituent magnetic stripe orders. The late-stage phase ordering also exhibits
a dynamical scaling symmetry. We further show that the annihilation of
dislocations follows a power-law time dependence with a logarithmic correction
that depends on magnetic fields. Implications of our results for SkL phases in
magnetic materials are also discussed.
