Effect of a Pt Interlayer on the Domain Dynamics in Ultrathin Co Layers with Perpendicular Anisotropy

The dynamics of domain walls in ultrathin Pt/Co(0.6 nm)/Pt(t)/Co(0.6 nm)/Pt heterostructures with perpendicular magnetic anisotropy, where 0 nm < t < 10 nm, is studied. A transition from correlated to independent magnetization reversal is revealed at a Pt interlayer thickness of t = 5.5 nm. In the transition region, the domain wall is found to slowdown and stop in the "soft" layer at a constant magnetic field, which indicates a change in the nature of interlayer coupling. It is established that the energy of exchange coupling between Co layers in the transition region is equal to similar to 17 mu J/m(2). Enhancement of the exchange coupling between the layers leads to the relaxation of magnetization in the "soft" layer and to magnetization in the "hard" layer when the external field is removed; in this case, the movement of the wall is described by an exponential function. The dynamics of domain walls with independent and coupled magnetization reversal of layers is considered; it corresponds to a creep mode in all cases at low fields. It is shown that the velocities of the walls for different layers are noticeably different and are due to the different roughness of interfaces.