Micromagnetics of magnetic chemical modulations in soft-magnetic cylindrical nanowires
Laura Álvaro-Gómez, Sandra Ruiz‐Gómez, Claudia Fernández‐González, Michael Schöbitz, Nicolas Mille, Jérôme Hurst, Dhananjay Tiwari, A. De Riz, Ingrid Marie Vincent Andersen, Julien Bachmann, L. Cagnon, Michael Foerster, Lucía Aballe, Rachid Belkhou, Jean-Christophe Toussaint, C. Thirion, Aurélien Massebœuf, D. Gusakova, Lucas Pérez, Olivier Fruchart
Abstract
We analyze the micromagnetics of short longitudinal modulations of a high-magnetization material in cylindrical nanowires made of a soft-magnetic material of lower magnetization such as permalloy, combining magnetic microscopy, analytical modeling, and micromagnetic simulations. The mismatch of magnetization induces curling of magnetization around the axis in the modulations, in an attempt to screen the interfacial magnetic charges. The curling angle increases with modulation length, until a plateau is reached with nearly full charge screening for a specific length scale ${\mathrm{\ensuremath{\Delta}}}_{\mathrm{mod}}$, larger than the dipolar exchange length of any of the two materials. The curling circulation can be switched by the Oersted field arising from a charge current with typical magnitude ${10}^{12}\phantom{\rule{0.28em}{0ex}}\mathrm{A}/{\mathrm{m}}^{2}$ for a diameter of $\ensuremath{\sim}100$ nm, and reaching a maximum for ${\mathrm{\ensuremath{\Delta}}}_{\mathrm{mod}}$.