Universality Classes of Magnetic Domain Wall Motion

Abstract

We examine magnetic domain wall motion in metallic nanowires Pt-Co-Pt. Regardless of whether the motion is driven by either magnetic fields or current, all experimental data fall onto a single universal curve in the creep regime, implying that both the motions belong to the same universality class. This result is in contrast to the report on magnetic semiconductor (Ga,Mn)As exhibiting two different universality classes. Our finding signals the possible existence of yet other universality classes which go beyond the present understanding of the statistical mechanics of driven interfaces.

Spin Hall torque magnetometry of Dzyaloshinskii domain walls

“…We find no such offset within the experimental uncertainty, which implies an upper limit βP = 0.02 ± 0.02. This is in contrast to βP > 1 inferred in similar materials where variations under in-plane fields were not considered [2,35,36]. These results disentangle SHE and STT in such materials, and show that here nonadiabatic STT plays a negligible role.…”

“…Figure 2 shows that H prop varies linearly with j e , indicating current acts as an easy-axis effective field H eff = χj eẑ that can assist or hinder DW propagation. Both nonadiabatic STT [2,35,36] and spin torque from the SHE [19][20][21]37] [25] is independent of , with χ STT = ± βP /2μ 0 |e| M s , where is the DW width, β is the nonadiabicity parameter, and positive (negative) corresponds to up-down (down-up) DWs such that current drives them in the same direction.…”

Magnetic domain-wall motion in a nanowire: Depinning and creep

“…This situation strongly motivates experimental 22 and theoretical [23][24][25] studies of the current-driven DW motion in metallic ferromagnets. This paper aims at theoretical explorations of this issue based on the observation that the DW anisotropy, characterizing the energy cost associated with the change in the tilting-angle of the magnetization inside a DW, is orders of magnitude larger in metallic ferromagnets than in ferromagnetic semiconductors.…”

Current-induced magnetic domain wall motion below intrinsic threshold triggered by Walker breakdown

“…We observe that the velocity of the domain wall motion is the vector sum of currentand field-induced velocities, and that the domain wall can be driven against the direction of a magnetic field as large as 2,000 Oe, even at currents below J th 0 . We show that this counterintuitive phenomenon is triggered by Walker breakdown 16 , and that the additive velocities provide a unique way of simultaneously determining the spin polarization of current and the Gilbert damping constant.Controlling the position of magnetic domain walls is crucial for spintronics devices such as racetrack memory [1][2][3][4][5][6][7][8][9][10][11][12][13][14][17][18][19][20] . The threshold current density, which determines the minimum current density necessary to trigger domain wall motion, has been considered a key parameter in diagnosing the controllability of devices, so its quantitative determination and reduction have become important topics.…”