Controlling injection and propagation of domain walls in magnetic nanowires
Abstract/Contents
- Abstract
- Magnetic domain walls (DWs) are regions where the magnetization changes rapidly from one orientation to another. These magnetic textures are of considerable interest both scientifically as well as technologically with potential applications in novel memory and logic devices based on their controlled creation and manipulation under magnetic field and current. We consider the injection and propagation of DWs in two different materials systems, namely in permalloy (Ni81Fe19) nanowires where the magnetization points in the film plane and in Co/Ni multilayers where the magnetization points perpendicular to the film plane. DWs in permalloy nanowires can be considered as composite objects composed of elementary topological bulk and edge defects with integer and fractional winding numbers, respectively; whose relative spatial arrangement determines the chirality of the DW. Here we show how we can understand and control the trajectory of DWs in magnetic branched networks, composed of connected nanowires, by a consideration of their fractional elementary topological defects and how they interact with those innate to the network. We also demonstrate a highly reliable mechanism for the injection of a DW of a given chirality into a nanowire and show that its chirality determines which branch the DW follows at a symmetric Y-shaped magnetic junction - the fundamental building block of the network. Using these concepts, we unravel the origin of the one-dimensional nature of magnetization reversal of connected artificial spin ice systems that have been observed in the form of Dirac strings. In the second part of this work, we demonstrate that by irradiating small regions in perpendicularly magnetized nanowires to induce in-plane magnetic anisotropy, and thereby creating a 90° DW, we can significantly decrease the energy needed for DW creation. In fact, due to the presence of a 90° DW at the injection site, the process of creating a DW in the nanowire in reality involves extraction of the 90° DW to the perpendicularly magnetized region. We show that this can not only be done by conventional means of creating local magnetic fields near the injection site but more importantly, by exploiting the giant spin transfer torque obtained at the 90° DW (due to the abrupt change in the magnetization), we can inject a series of domain walls using nano-second long, uni-polar current pulses through the nanowire which use much lower energy than conventional techniques.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2013 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Phung, Timothy |
|---|---|
| Associated with | Stanford University, Department of Electrical Engineering. |
| Primary advisor | Harris, J. S. (James Stewart), 1942- |
| Thesis advisor | Harris, J. S. (James Stewart), 1942- |
| Thesis advisor | Howe, Roger Thomas |
| Thesis advisor | Parkin, Stuart S. P |
| Thesis advisor | White, Robert |
| Advisor | Howe, Roger Thomas |
| Advisor | Parkin, Stuart S. P |
| Advisor | White, Robert |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Timothy Phung. |
|---|---|
| Note | Submitted to the Department of Electrical Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2013. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2013 by Timothy Phung
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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