Crossed-Ratchet Effects for Magnetic Domain Wall Motion

Abstract

We study both experimentally and theoretically the driven motion of domain walls in extended amorphous magnetic films patterned with a periodic array of asymmetric holes. We find two crossed-ratchet effects of opposite sign that change the preferred sense for domain wall propagation, depending on whether a flat or a kinked wall is moving. By solving numerically a simple phi(4) model we show that the essential physical ingredients for this effect are quite generic and could be realized in other experimental systems involving elastic interfaces moving in multidimensional ratchet potentials.

Crossed-ratchet effects and domain wall geometrical pinning

“…For extended DW this kind of pinning has been recently realized experimentally and showed to be able to modify the magnetization dynamics 7,16,[18][19][20] and to produce, in particular, interesting ratchet transport of magnetic DW. 3,24 Being mostly geometrical (i.e., determined mostly by the shape and distribution of holes or by the geometry of the boundaries and not much by the specific microscopic pinning interaction) this kind of pinning has the advantage over other artificial pinning mechanisms that it can be more easily tailored at a wide range of scales to control the wall motion in various specific ways.…”

“…The crossed rectification reported in Ref. 3 relies on the difference between the critical fields to depin the wall in each direction, and it is also present in a generic model for elastic interfaces: the φ 4 model. 25 In this paper we calculate the depinning field of a generic φ 4 interface in the presence of an array of triangular antidots by both geometrical considerations and numerical simulations.…”

“…Prominent examples are the propagation of reaction fronts or surface growth in material science, 1 cell motility and membrane dynamics in biology, 2 domain walls (DW) in ferromagnetic [3][4][5][6][7][8] or ferroelectric films, [9][10][11] fluid invasion in porous media, 12 contact lines of liquids menisci, 13 and crack propagation. 14,15 In all these cases, the presence of heterogeneities, which locally promote wandering, compete with the elasticity of the interface, giving rise to complex collective pinning effects.…”

“…We use this simple model because it is the minimum model that captures the essential physics behind the crossed-ratchet effects reported in Ref. 3: the competition between pinning and driving forces on a one-dimensional (1D) elastic interface that propagates in a two-dimensional (2D) array of asymmetric pinning centers. Actually, numerical simulations using the complete micromagnetic formulation provide qualitatively the same results.…”

Closure magnetization configuration around a single hole in a magnetic film

“…2 One common feature in many of these magnetic nanostructures, such as magnetic nanorings, [3][4][5][6] thin films patterned with arrays of antidots, [7][8][9][10][11][12] or magnetic disks with controlled defects, 13 is the existence of nonmagnetic holes within the magnetic material. Most of the attention has been devoted to the analysis of the different magnetic configurations corresponding to each different kind of structure, such as the transitions between in-plane axial and vortex states in nanorings, 14 or the different kinds of periodic closure domain structures in magnetic films with antidots.…”