Controlling Domain-Wall Nucleation in Ta / Co - Fe - B / MgO Nanomagnets via Local Ga+ Ion Irradiation
Year: 2021
Type: article
Abstract: Comprehensive control of the domain-wall nucleation process is crucial for spin-based emerging technologies ranging from random-access and storage-class memories through domain-wall logic concepts to nanomagnetic logic. In this work, focused ${\mathrm{Ga}}^{+}$ ion irradiation is investigated as an effective means to control domain-wall nucleation in $\mathrm{Ta}$/$\mathrm{Co}$-$\mathrm{Fe}$-$\mathrm{B}$/$\mathrm{Mg}\mathrm{O}$ nanostructures. We show that, analogously to ${\mathrm{He}}^{+}$ irradiation, it is not only possible to reduce the perpendicular magnetic anisotropy but also to increase it significantly, enabling bidirectional manipulation schemes. First, the irradiation effects are assessed at the film level, sketching an overview of the dose-dependent changes in the magnetic energy landscape. Subsequent time-domain nucleation characteristics of irradiated nanostructures reveal substantial increases in the anisotropy fields but surprisingly small effects on the measured energy barriers, indicating shrinking nucleation volumes. Spatial control of the domain-wall nucleation point is achieved by employing focused irradiation of preirradiated magnets, with the diameter of the introduced circular defect controlling the coercivity. Special attention is given to the nucleation mechanisms, changing from the coherent radiation of a Stoner-Wohlfarth particle to depinning from an anisotropy gradient. Dynamic micromagnetic simulations and related measurements are used in addition to model and analyze this depinning-dominated magnetization reversal.
Source: Physical Review Applied
Institutions: Technical University of Munich, Politecnico di Torino
Language: Latvian
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W3132659901