Localized magnetic inhomogeneities generation on defects as a new channel of damping for a moving domain wall

Abstract

The paper presents theoretical studies on the domain wall energy losses that arise when it moves through the magnetic defect region. These losses are largely related to the generation of localized magnetization waves in the defect region. It is shown that the process of the domain wall energy scattering on the defect can be regarded as a new "channel of damping" for a domain wall. The study was carried out using numerical and analytical methods through the example of a three-layer model of the ferromagnetic structure, in which the intermediate layer differs in its physical parameters from the rest of the crystal. The intermediate layer (or magnetic defect) was simulated by a spatial modulation of the magnetic parameters. The modes of motion, in which "effective damping" is minimal, were calculated. The damping value depends on the excitation energy of the localized waves and is determined by the ratio of the defect properties and initial velocity of the domain wall motion. It is specifically shown that an increase in the domain wall energy loss is associated with the increase in the localized waves oscillations amplitude. In this case, the dependence of the localized waves oscillations amplitude on the domain wall initial velocity only has one maximum. It is at this point that the domain wall energy losses are maximal. They can be significantly reduced if the domain wall velocity is noticeably higher or lower than the maximum. This behavior was studied for both the point and extended defects.

One-dimensional dynamics of the domain boundary in a multilayer ferromagnetic structure

“…In this case the DW should change its shape significantly when passing through the thin magnetic layer. In these systems pinning of domain walls, generation of localized magnetization waves, such as magnetic solitons and breathers, generation of spin waves are possible [7,12,14,[23][24]. It is worth to note that two-dimensional magnetic inhomogeneities of magnetic vortex type near the inhomogeneities of the magnetic anisotropy also demonstrate a diversity of their behavior: pinning of the vortex by defect with explicit change in the rotation speed, reflection before defect with different motion paths, etc.…”

External magnetic field control of the magnetic breather parameters in a three-layer ferromagnetic structure

“…В связи со сложностью задачи, даже для одномерного случая, исследователями рассматривалась, как правило, модуляция лишь отдельных параметров магнитной системы. Часто учитывалась, например, модуляция магнитной анизотропии [15,16,20]. При определённых условиях, изучение одномерной динамики магнитных неоднородностей приводит к интересной и с математической точки зрения задаче нахождения решения нелинейного дифференциального уравнения типа синус-Гордона с переменными коэффициентами, имеющего важное значение для многих областей современной физики [21].…”

Excitation of Large-Amplitude Localized Nonlinear Waves by the Interaction of Kinks of the Sine-Gordon Equation with Attracting Impurity

“…The work [22] has shown that this effect can be observed under certain conditions even in the presence of damping that always occurs in real physical systems. The value of energy consumed for the excitation of localized waves by the kink will determine the value of a new contribution to the effective damping of a moving kink [45]. It may change depending on its initial velocity.…”