Magnetic domain-wall velocity oscillations in permalloy nanowires

Abstract

Oscillations of the field-driven domain-wall ͑DW͒ velocity in permalloy nanowires are observed above the Walker breakdown condition using high-speed magneto-optic polarimetry. A one-dimensional analytical model and numerical simulations of DW motion and spin dynamics are used to interpret the experimental data. Velocity oscillations are shown to be much more sensitive to properties of the DW guide structure ͑which also affect DW mobility͒ than the DW spin precessional frequency, which is a local property of the material. The results demonstrate the feasibility of experimentally probing the complex field-driven DW dynamics in magnetic nanowires, thereby testing the validity of theoretical models and numerical simulations that describe the dynamics.

Domain wall motion in magnetic nanowires: an asymptotic approach

“…This approach has had numerous applications to domain wall motion in various regimes, and the results agree well with both numerical simulations and experiments [18][19][20][21][22][23][24][25][26]. However, from a mathematical point of view, this approach is ad hoc, and difficult to justify; the approximation is uncontrolled, and it is unclear how to obtain corrections to it.…”

Statics and field-driven dynamics of transverse domain walls in biaxial nanowires under uniform transverse magnetic fields

“…Therefore, the solution of the zero-order equations is just Eqs. (16) and (27), with boundary conditions (12) and (14). To obtain the TDW propagation velocity, we need to proceed to the next order.…”

“…Magnetic DWs can be basic bit units in modern logical [1] and storage [2,3] devices. By applying various driving factors, such as magnetic fields [4][5][6][7][8][9][10][11][12][13][14][15], spin-polarized currents [16][17][18][19][20][21][22][23][24], or temperature gradients [25][26][27][28][29], etc, DWs can be driven to move along wire axis with quite high velocity, which results in high processing speed of devices based on them. Traditionally, the time evolution of the magnetization distribution is described by the nonlinear Landau-Lifshitz-Gilbert (LLG) equation [30].…”

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

“…The uniformly propagating stationary mode (Region I, H < H c ) is well understood, 11,12,23 (Walker solution). The complex oscillatory motion for H c (Region II) has been explored numerically 20,21 and experimentally 22 . The simulated displacement of an oscillatory mode [illustrated as a displacement record in Fig.…”

“…High-bandwidth magneto-optic polarimetry 24 was used to measure the time-dependent DW displacements under a combination of longitudinal drive field H and transverse bias field H bias strengths. One advantage of using polarimetry to track DW displacements by time-of-flight techniques (and also instantaneous velocity by measuring the transient response 22 as a DW sweeps across the polarimeter light spot) is that the mobility curves can be directly measured. A short injection pulse initiates DW propagation down the nanowire conduit and the velocity (both average and instantaneous at a prescribed point) can be measured for any combination of static longitudinal and transverse bias magnetic fields.…”