One-dimensional dynamics of magnetic inhomogeneities in a three-layer ferromagnetic structure with different values of the magnetic parameters

摘要

In this paper, we considered a three-layer ferromagnetic structure, which consists of two broad layers separated by a thin layer. The parameters of magnetic anisotropy, exchange and damping are considered functions of the coordinate directed perpendicular to the interface of the layers. The case of a point magnetic defect described with the help of the Dirac delta-function is studied with the values of the parameters of magnetic anisotropy, exchange and damping, which differ from the values of the analogous parameters in the remaining magnet. The dynamics of the domain wall is studied theoretically with allowance for the excitation of localized magnetization waves in the region of the magnetic defect. Using the collective-coordinate approach, a system of two equations is obtained for the coordinate of the DW center and the amplitude of the oscillations of the magnetization wave localized in the defect region. From the analysis of this system of equations, it is found how the inhomogeneity of the damping and exchange parameter affects the dynamics of magnetic inhomogeneities. The value of the effective dissipation coefficient is determined, which for the case of motion of the domain wall now becomes dependent on the position of the domain wall. It is shown that accounting for heterogeneity of dissipation and exchange can significantly change the speed and scenario of the dynamics of the DW. The dependence of the minimum value of the magnetic field on the dissipation and exchange inhomogeneity coefficients, at which the DW passes through the defect region, is found.