Fast domain wall dynamics in magnetic nanotubes: Suppression of Walker breakdown and Cherenkov-like spin wave emission

Abstract

We report on a micromagnetic study on domain wall (DW) propagation in ferromagnetic nanotubes. It is found that DWs in a tubular geometry are much more robust than ones in flat strips. This is explained by topological considerations. Our simulations show that the Walker breakdown of the DW can be completely suppressed. Constant DW velocities above 1000 m/s are achieved by small fields. A different velocity barrier of the DW propagation is encountered, which significantly reduces the DW mobility. This effect occurs as the DW reaches the phase velocity of spin waves (SWs), thereby triggering a Cherenkov-like emission of SWs.

Magnetic interactions and reversal mechanisms in Co nanowire and nanotube arrays

“…The ability to control the NW/NT dimensions (length, inner/outer diameters, and wall thickness), the array configuration and interwire distance, allows the tuning of different energies (magnetostatic, magnetocrystalline, and exchange) to obtain novel phenomena induced by nanoscopic confinement or proximity effects. [5][6][7][8][9] A thorough understanding of the magnetic properties of NW and NT arrays with tailored geometries is of extreme importance for their implementation in future applications. In particular, new insights on the magnetostatic interactions between nanoelements will highly influence the design of improved devices using magnetic arrays.…”

Suppression of Walker breakdown in magnetic domain wall propagation through structural control of spin wave emission

“…In contrast, nanowire edge roughness has shown improved DW dynamics by distorting the vortex core nucleation process at the nanowire edges. 16,17 The removal of the edges in simulations by forming tubular nanowires with periodic boundaries has shown improved DW dynamics; 18,19 however, the geometrical complexity of tubular nanostructures is incompatible with conventional nanoscale lithographic fabrication, and therefore this approach is not suitable as a mode of control for technological applications.…”

Walker regime for walls in ferromagnetic nanotubes

“…Such devices are modeled by a 1d-Landau-Lifschitz equation, and existence and stability of one-wall profiles are established (see [10,11,12,21] and the references therein). In [24], the authors propose to use ferromagnetic nanotubes instead of ferromagnetic nanowires or nano strips in order to deal with domain wall motion in the Walker regime, which is stabler and more reliable for applications. In the present work we exhibit a 2d-model for ferromagnetic nanotubes and we study domain wall dynamics in this model for a small applied magnetic field.…”

“…We deal with domain wall profiles in the Walker regime as in [24]. For a vanishing applied field (h a = 0), we observe the formation of domains in which the magnetization is along the tube axis.…”