Creation and propagation of a single magnetic domain wall in 2D nanotraps with a square injection pad

Abstract

Polycrystalline permalloy 2D nanotraps with a thickness of 20 nm were studied using a Lorentz microscope associated with micro-magnetic simulations. Each trap was designed to create a single head-to-head domain wall. The traps consist of a few nanowires with an in-plane dimension of w nm × 1000 nm (w = 150, 200 and 250 nm). Some structures with an injection pad were also designed to create a single domain wall and propagate it through the structure with the said injection pad. A few of them were patterned to study the nucleation and propagation behavior of such nucleated domain walls using both horizontal magnetic field and injection pad approaches. The case of a domain wall created at the first corner of the trap with a wire width of 200 nm was systematically studied, while single and multiple domain walls can also be created and propagated with or without an injection structure. The characteristics of such movements were exploited with an emphasis on a single head-to-head domain wall.

Magnetic Domain Walls Moving in Curved Permalloy Nanowires under Continuous and Pulsed Fields

“…The patterned DWT with a square injection was also characterized using the pulsed field method [18], this method integrated in the Lorentz CM20. Herein, various bundles of field pulses are generated with a certain time-period, µs or ns.…”

“…The stage of those Au-wires is fixed and paralleled to the substrate/sample surface. The maximum pulsed field of 200 Oe could be generated in the sample plane with the duration range of 0.1-5 µs [18]. Using the combination of these continuous and pulsed field methods is useful to understand the domain wall behaviour and responses of the given structures with both static and pulsed fields.…”

Strain-controlled Domain Wall injection into nanowires for sensor applications

“…At the same time, uncontrolled nucleation of domain walls at higher fields needs to be avoided, thus setting the maximum operation field value. Previous studies about DW sensors investigated the propagation and nucleation fields, and showed how they depend on material parameters and device geometry [7][8][9][10][11][12] . While the field operation window in idealized operation conditions is known, in real devices further factors play a role and have been previously neglected.…”

“…Strain in magnetic materials is known to induce a preferential direction of magnetization (anisotropy) due to magnetoelastic coupling 14,15 and even pin a DW in a nanowire 16 . In DW based devices, a common approach to generate a DW is to use a larger magnetic (nucleation) pad attached to the nanowire exploiting the reduced shape anisotropy 12,17,18 as shown in figure 1. It has been shown recently using simulations how, in the nucleation pad, straininduced anisotropy can overcome the shape anisotropy governing the switching of the magnetic state 19 .…”