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We report the current-induced domain-wall (CIDW) motion along the electron flow in the perpendicularly magnetized Co/Ni/Co structure sandwiched between the top and bottom Pt layers, observed by means of the Kerr microscope. As the lower Co thickness increases, the DW velocity for the electron flow is significantly increased, and also its motion becomes more stable irrespective of various current pulses. From the longitudinal field dependence of the DW velocity, it is found that the increase of the lower Co thickness increases a Dyzaloshinskii–Moriya interaction in the bottom Co/Pt interface, which results in the increase of the chiral spin torque, responsible for the increase of the DW velocity along the electron flow. [ABSTRACT FROM PUBLISHER]

Spin-polarized currents provide a powerful means of manipulating the magnetization of nanodevices, and give rise to spin transfer torques that can drive magnetic domain walls along nanowires. In ultrathin magnetic wires, domain walls are found to move in the opposite direction to that expected from bulk spin transfer torques, and also at much higher speeds. Here we show that this is due to two intertwined phenomena, both derived from spin-orbit interactions. By measuring the influence of magnetic fields on current-driven domain-wall motion in perpendicularly magnetized Co/Ni/Co trilayers, we find an internal effective magnetic field acting on each domain wall, the direction of which alternates between successive domain walls. This chiral effective field arises from a Dzyaloshinskii-Moriya interaction at the Co/Pt interfaces and, in concert with spin Hall currents, drives the domain walls in lock-step along the nanowire. Elucidating the mechanism for the manipulation of domain walls in ultrathin magnetic films will enable the development of new families of spintronic devices. [ABSTRACT FROM AUTHOR]

Abstract: We report an asymmetry of magnetic disorder in exchange-biased IrMn(t IrMn=5–20nm)/CoFe(50nm) films observed by means of a Kerr microscope, capable of direct domain observation. From the correlation between the magnetization half-reversal time and applied magnetic field, we find that the magnetization switching in all the films occurs via a thermally activated reversal mechanism for both branches of hysteresis loops. Surprisingly, in the forward branch reversal where the applied magnetic field is antiparallel to the direction of exchange-bias field, degree of magnetic disorder decreases as exchange-bias field increases, which is definitely contrasted with the case of backward branch reversal. This result is likely ascribed to the fact that the local values of exchange-bias field and coercive field are oppositely fluctuating with each other in the film. [Copyright &y& Elsevier]

In this study, we investigated the stochastic nature of domain reversal dynamics in exchange-biased IrMn/CoFe film using a time-resolved Kerr microscope. Interestingly, the statistical distributions of the magnetization half-reversal times for both forward and backward applied fields show that the magnetization reversal dynamics is much more stochastic for the backward branch, where an applied field is parallel to the exchange-bias field direction. The enhanced stochasticity is ascribed to the large degree of magnetic disorder during backward reversal, which induces discrete and random Barkhausen jumps, whereas the forward branch reversal is dominated by a thermally activated depinning process caused by a single potential barrier. This result can be explained by the asymmetry of the magnetic disorder between both branches of a hysteresis loop. [ABSTRACT FROM AUTHOR]

We have investigated the Barkhausen critical scaling behavior of NixFe1-x (x = 0-0.5) films using a magneto-optical microscope, capable of time-resolved domain observation. Real-time direct observations of the domain evolutions in these films revealed that magnetization reversal occurred with a sequence of random Barkhausen jumps. From more than 1000 repeated experiments with each sample, it was found that the distribution of the Barkhausen jump size followed a power-law distribution. The scaling exponent of the power-law distribution was found to have the same value of 1.1, independent of the film composition, revealing a universal critical scaling behavior in these alloy films. [ABSTRACT FROM AUTHOR]

We demonstrate a highly efficient and simple scheme forinjecting domain walls into magnetic nanowires. The spin transfertorque from nanosecond long, unipolar, current pulses that cross a90° magnetization boundary together with the fringing magneticfields inherently prevalent at the boundary, allow for the injectionof single or a continual stream of domain walls. Remarkably, the currentsneeded for this “in-line” domain wall injection schemeare at least one hundred times smaller than conventional methods. [ABSTRACT FROM AUTHOR]