Generation of Intense and Fast Magnetic Field Pulses Through Domain Wall Displacements in Planar Nanoconduits

In recent years the magnetization reversal processes and their dynamics at the nanoscale have been intensively studied in nanostructured magnetic materials [1]. This development can be achieved mainly due to the new nanofabrication and characterization methods that allow accessing new regimes in size and time resolution scales [2]. At the same time, our limited knowledge of the magnetization dynamics in these regimes needs to be expanded to implement magnetic devices. Despite all past and present research efforts there are still many open questions and challenges that need to be solved in order to fully understand and control magnetism on very small length and very fast time scales.<br/>When studying thin-film magnetic nanostructures, which are the main interest for applications, high-speed measurements of the magnetization dynamics can be performed by means of sub-nanosecond magneto-optic sampling techniques [3]. Nevertheless, generating intense and fast magnetic field pulses to be used in such studies is still a difficult experimental challenge.<br/>In this work a pathway to generate intense and fast magnetic field pulses through domain wall displacement in nanoconduits is proposed. 150 nm wide and 13 nm thick planar conduits (nanostripes) made of Permalloy are used to propagate domain walls (DWs), whose displacement creates magnetic field pulses that affect the magnetization of magnetic nanoellipses also made of Permalloy, with dimensions 425x170x13 nm³, that are placed in the proximities of the nanostripe. The approach exploits the fact that magnetic DWs can produce magnetic field pulses as intense as up to 2 KOe. Due to their extremely confined geometry and the fast displacement velocities that can be obtained with these confined geometries, intense magnetic field pulses in the sub-ns regime are produced by the domain walls. The temporal profile and strength of the magnetic field pulses created by the transverse domain wall during its displacement over the conduit has been analyzed in detail. The effect of such field pulses on nanoellipses placed at 50 nm from the domain wall conduit has been studied, finding specific situations in which a field pulse assisted magnetization reversal is observed in neighboring nanoellipses. Extensions on this work may lead, for example, to the fabrication of domain wall conduits with more complex shapes, where the combined displacement of several domain walls can be used to increase the field pulse intensity as well as for shaping the field pulse, beyond what was achieved using simply shaped conduits, towards their implementation in information storage applications.<br/><br/>[1] R. Streubel <i>et al</i>, J. Phys. D: Appl. Phys. 49 363001 (2016)<br/>[2] A. Fernández-Pacheco, R. Streubel, O. Fruchart <i>et al.</i> Nat Commun 8, 15756 (2017)<br/>[3] T.J. Hayward and K.A. Omari, J. Phys. D: Appl. Phys. 50 084006 (2017)