Structure of head-to-head domain wall in cylindrical amorphous ferromagnetic microwire and a method of anisotropy coefficient estimation

Abstract

A model of head-to-head domain wall in the cylindrical amorphous ferromagnetic microwire is proposed by treating a class of exact particular solutions of Landau-Lifshitz-Gilbert equation in cylindrical coordinates, which are obtained for appropriate boundary conditions. It is shown that both the magnetic anisotropy coefficient value in the center of cross-section and the rate of its value change along the radius directly determine the domain wall structure. A flexural planar domain wall is visualized and analyzed under the influence of various parameters of the microwire. A method of anisotropy coefficient estimation is developed: the derived formula for mobility is used to evaluate values of anisotropy coefficient of the wire near its symmetry axis, the length of the head-to-head domain wall can be used for evaluation of radial dependence of anisotropy coefficient. For extraction of anisotropy coefficient the dynamic properties of the head-to-head domain wall propagation are investigated experimentally for microwires with different anisotropy coefficients: in stressed state and after partially stress removed state. The theory fit the measurements with linear dependence of the velocity on the magnetic field. The particular case of planar domain wall, corresponding to radial independent anisotropy coefficient, is also shown for a comparison.