Temperature Dependence of the Kinetics of Domain-Structure Transformation in Heterophase Co/Pt/Co Films

Using Kerr microscopy, the effect of temperature on the displacement of domain boundaries in ultrathin exchange-coupled ferromagnetic layers in heterophase Pt/Co/Pt/Co/Pt films with perpendicular magnetic anisotropy and a nonmagnetic wedge-shaped spacer layer is experimentally studied. The exchange interaction between the Co layers is investigated for spacer-layer thicknesses ranging from 5 to 6 nm within the temperature range of 200 to 300 K. The independent displacement of domain boundaries in the Co layers under the action of a perpendicular magnetic field applied to the sample surface occurs within the range of thicknesses d(0) < d < d(CR). Throughout the entire temperature range, the displacement of domain boundaries along the Pt wedge results in their stabilization in an equilibrium position. This position depends on the magnitude of the applied field, the thickness of the nonmagnetic spacer layer, and temperature. It is determined by the balance of forces acting on the boundary, including the external field, the effective exchange field between the Co layers, and the coercivity field. Upon the removal of the external field, the domain boundaries relax to the initial state with d = d(0) due to the effect of the exchange field. The characteristics of this relaxation depend on the temperature. The study of the mechanism of domain-boundary stabilization near d(CR) reveal that the critical thickness of the nonmagnetic spacer layer d(CR) and the coercivity field exhibit oppositely directed dependences on temperature.