  We present multi-scale dynamical simulations of voltage-induced
insulator-to-metal transition in the double exchange model, a canonical example
of itinerant magnet and correlated electron systems. By combining
nonequilibrium Green's function method with large-scale Landau-Lifshitz-Gilbert
dynamics, we show that the transition from an antiferromagnetic insulator to
the low-resistance state is initiated by the nucleation of a thin ferromagnetic
conducting layer at the anode. The metal-insulator interface separating the two
phases is then driven toward the opposite electrode by the voltage stress,
giving rise to a growing metallic region. We further show that the initial
transformation kinetics is well described by the Kolmogorov-Avrami-Ishibashi
model with an effective spatial-dimension that depends on the applied voltage.
Implications of our findings for the resistive switching in colossal
magnetoresistant materials are also discussed.
