Magnetic domain-wall velocity enhancement induced by a transverse magnetic field

Abstract

Spin dynamics of field-driven domain walls (DWs) guided by Permalloy nanowires are studied by high-speed magneto-optic polarimetry and numerical simulations. DW velocities and spin configurations are determined as functions of longitudinal drive field, transverse bias field, and nanowire width. Nanowires having cross-sectional dimensions large enough to support vortex wall structures exhibit regions of drive-field strength (at zero bias field) that have enhanced DW velocity resulting from coupled vortex structures that suppress oscillatory motion. Factor of ten enhancements of the DW velocity are observed above the critical longitudinal drive-field (that marks the onset of oscillatory DW motion) when a transverse bias field is applied. Nanowires having smaller cross-sectional dimensions that support transverse wall structures also exhibit a region of higher mobility above the critical field, and similar transverse-field induced velocity enhancement but with a smaller enhancement factor. The bias-field enhancement of DW velocity is explained by numerical simulations of the spin distribution and dynamics within the propagating DW that reveal dynamic stabilization of coupled vortex structures and suppression of oscillatory motion in the nanowire conduit resulting in uniform DW motion at high speed.

Engineering of Magnetic Softness and Domain Wall Dynamics of Fe-rich Amorphous Microwires by Stress- induced Magnetic Anisotropy

“…Recently we have reported that stress annealing of Fe-rich microwires results in induced transverse magnetic anisotropy that can be beneficial for further DW velocity improvement 36,37,43,44 . Therefore, we performed stress annealing of the Fe 75 B 9 Si 12 C 4 microwire.…”

“…We can assume that this outer domain shell with transverse magnetic anisotropy affects the travelling DW in a similar way as application of transversal bias magnetic field allowing enhancement the DW velocity 36,37,42,43 .…”

“…One of the possibilities related to the internal stresses relaxation in highly magnetostrictive Fe-rich microwires allowed considerable DW velocity and mobility enhancement 31,33 . Alternatively, theoretically and experimentally was shown that the DW velocity in a variety of groups of magnetic microwires can be considerably improved under application of transversal bias magnetic field 36,37,42,43 . Effect of transversal magnetic field on DW velocity is discussed considering the influence of transverse magnetic anisotropy on DW dynamics, influence of transverse field on spin precession and change of the DW width 42,43 .…”

Spin distributions and dynamics in domain walls guided by soft magnetic nanowire structures

“…The stretching mode is not one of the compact DW configurations and is a special type of mode that is affected dramatically by an applied magnetic field perpendicular to the nanowire axis and the thickness axis. This mode has been described in detail in prior publications [28], and will be briefly discussed in Section VI that outlines experimental evidence for the various modes described above. Mobility curves exhibit systematic temperature dependent shifts that are similar to static magnetic bias-field shifts reported in prior publications [28] and which are consistent with shifts of measured mobility curves described later.…”

“…The average forward motion of the core is slowed by the oscillatory displacement along the wire as H increases which accounts for the negative differential mobility. This region of complex oscillatory motion has been explored experimentally [8,10] and theoretically by analytical models [10] and by prior numerical simulations [10,22,28].…”