Transformation of the Domain-Wall Structure in Permalloy Nanotape Under Electrical Current Pulses

Abstract

Motion of the magnetic domain walls under the pulses of magnetic field or spin-polarized electric current is studied experimentally by direct visualization of the walls. The experiments are performed in the temperature range from 300 down to 6 K. Coercivity, mobility of the walls, and their variations with temperature are investigated. Wall velocity is observed to increase by orders of magnitude due to cooling from room to helium temperature in the case of current stimulated motion. The velocity becomes as high as the Walker velocity limit, about 1000 m/s. The walls are found to expand and tilt under the current pulses, which leads to their transformation into the domains with transverse magnetization.Index Terms-Magnetic circuits, magnetic domain-wall motion, momentum transfer, spin-polarized current, spin-transfer torque.

Effect of the shape and lateral dimensions on the magnetization reversal in permalloy nanofilms

“…Even hysteresis properties of the hybrid structures could be determined by the type of the domain wall [7] which, in turn, is determined not only by the material properties but by the thickness of the films, by the aspect ratio of the structures, by the proximity effects and by quality of the interface [8,9]. Recently we have observed unusual transformation of the walls into the macrodomain with transverse magnetization during their motion along the narrow permalloy stripes under the spin-polarized current which flows along the stripes [10]. The attempts to explain the effect put a question about the structure of the domain wall in narrow permalloy stripes, which also motivated our study.…”

Exchange spring-like inhomogeneous states in a ferromagnetic wire with current

“…(The exact calculation of such phenomena is rather complicated due to the three-dimensional nature of the problem). The residual displacement of the domain wall after its deformation under the action of a current pulse was repeatedly observed experimentally [34][35][36][37][38][39][40][41][42][43][44], but at that time the asymmetry mechanism was not clear, which led to the rapid development of the concept of " electron pressure" [45]. The mechanism proposed in this article automatically explains many experimentally observed features, for example, the presence of a current threshold, the stochasticity of the wall displacement, the rearrangement of the wall from transverse to longitudinal, the generation of new boundaries, etc.…”

“…Expression (19), which is true at a current density much lower than the critical value, formally describes the current-linear dynamics of the domain wall, the mechanism of which, as in the case of the pseudo-Hall effect, has nothing to do with the assumed spin polarization of current carriers. Over the past decades, an exceptionally large array of experimental data has been accumulated on the interaction of the magnetization of a ferromagnetic layer with electric current [34][35][36][37][38][39][40][41][42][43]. Particular attention is paid to two areas: the actual transport properties of layered systems and the motion of domain walls.…”

“…The mechanism proposed in this article automatically explains many experimentally observed features, for example, the presence of a current threshold, the stochasticity of the wall displacement, the rearrangement of the wall from transverse to longitudinal, the generation of new boundaries, etc. [34][35][36][37][38][39][40][41][42][43][44]. As for the numerical values, the estimate by formula (19) gives a greatly underestimated relative to the experimental value of the velocity of the order of 1 m/s.…”