The magnetization dynamics equation predicts that a domain wall that changes structure should undergo a displacement by itself - automotion - due to the relaxation of the linear momentum that is associated with the wall structure. We experimentally demonstrate this effect in soft nanostrips,transforming under spin transfer torque a metastable asymmetric transverse wall into a vortex wall. Displacements more than three times as large as under spin transfer torque only are measured for 1~ns pulses. The results are explained by analytical and numerical micromagnetics. Their relevance to domain wall motion under spin transfer torque is emphasized.
Equilibrium magnetization distribution of the vortex state magnetic nanoparticle is affected by the influence of the spin-transfer torque: an off-center out--of--plane vortex appears in the case of the disk shape particle and pure planar vortex in the case of asymmetric ring shape particle. The spin current causes extra out-of-plane magnetization structures identical to well known dip structures for the moving vortex. The shape of the dip structure depends on the current strength and value of the off-center displacement and it does not depend on the vortex polarity. The critical current depend…
We investigate the dynamics of a magnetic vortex driven by spin-transfer torque due to spin current in the adiabatic case. The vortex core represented by collective coordinate experiences a transverse force proportional to the product of spin current and gyrovector, which can be interpreted as the geometric force determined by topological charges. We show that this force is just a reaction force of Lorentz-type force from the spin current of conduction electrons. Based on our analyses, we propose analytically and numerically a possible experiment to check the vortex displacement by spin curren…
There is a storied scientific history in the role of mechanical instruments for the measurement of fundamental physical interactions. Among these include the detection of magnetic torques via a displacement of a compliant mechanical sensor as a result of angular momentum transfer. Modern nanofabrication methods have enabled the coupling of mechanical structures to single, miniature magnetic specimens. This has allowed for strikingly sensitive detection of magnetic hysteresis and other quasi-static effects, as well as spin resonances, in materials confined to nanoscale geometries. The extraordi…
In magnetic wires with perpendicular anisotropy, moving domain with only current or only circularly polarized light requires a high power. Here, we propose to reduce it by using both short current pulses and femtosecond laser pulses simultaneously. The wires were made out of perpendicularly magnetized film of Pt/Co/Ni/Co/Pt. The displacement of the domain wall is found to be dependent on the laser helicity. Based on a quantitative analysis of the current-induced domain wall motion, the spin orbit torque contribution can be neglected when compared to the spin transfer torque contribution. The e…
We demonstrate numerically the ability to displace a magnetic domain wall by a remote spin current injection. We consider a long and narrow magnetic nanostripe with a single domain wall (DW). The spin-polarized current is injected perpendicularly to the plane of the film (CPP) through a small nanocontact which is located at certain distance from the domain wall initial position. We show theoretically that the DW motion can be initiated not only by conventional spin-transfer torque but also by indirect spin-torque, created by a remote spin-current injection and then transferred to the DW by the…
The dynamics of a magnetic domain wall in a semi circular nanowire loop is studied by an analytical model and micromagnetic simulations. We find a damped sinusoidal oscillation of the domain wall for small displacement angles around its equilibrium position under an external magnetic field in the absence of currents. By studying the effect of current induced nonadiabatic spin transfer torque on the magnetic domain wall resonance frequency and mass, a red shift is found in the resonance frequency and domain wall mass increases by increasing the ratio of nonadiabatic spin torque to adiabatic con…
Memristors are non-volatile nano-resistors. Their resistance can be tuned by applied currents or voltages and set to a large number of levels between two limit values. Thanks to these properties, memristors are ideal building blocks for a number of applications such as multilevel non-volatile memories and artificial nano-synapses, which are the focus of this work. A key point towards the development of large scale memristive neuromorphic hardware is to build these neural networks with a memristor technology compatible with the best candidates for the future mainstream non-volatile memories. He…
Domain wall motion driven by ultra-short laser pulses is a prerequisite for envisaged low-power spintronics combining storage of information in magneto electronic devices with high speed and long distance transmission of information encoded in circularly polarized light. Here we demonstrate the conversion of the circular polarization of incident femtosecond laser pulses into inertial displacement of a domain wall in a ferromagnetic semiconductor. In our study we combine electrical measurements and magneto-optical imaging of the domain wall displacement with micromagnetic simulations. The optic…
The induced motion of a magnetic vortex in a micron-sized ferromagnetic disk due to the DC current injection is studied by measuring planar Hall effect. The DC current injection is found to induce the spin torque that sweeps the vortex out of the disk at the critical current while bias magnetic field are applied. The current-induced vortex core displacement deduced from the change in planar Hall resistance is quantitatively consistent with theoretical prediction. Peak structures similar to those originated from spin wave excitations are observed in the differential planar Hall resistance curve…
In this paper, we study the domain wall motion induced by vertical current flow in asymmetric magnetic tunnel junctions. The domain wall motion in the free layer is mainly dictated by the current-induced field-like torque acting on it. We show that as we increase the MTJ asymmetry, by considering dissimilar ferromagnetic contacts, a linear-in-voltage field-like torque behavior is accompanied by an enhancement in the domain wall displacement efficiency and a higher degree of bidirectional propagation. Our analysis is based on a combination of a quantum transport model and magnetization dynamics…
We consider the spin-current driven dynamics of a magnetic nanostructure in a conductive magnetic wire under a heat gradient in an open circuit, spin Seebeck effect geometry. It is shown that the spin-current scattering results in a spin-current torque acting on the nanostructure and leading to precession and displacement. The scattering leads also to a redistribution of the spin electrochemical potential along the wire resulting in a break of the polarity-reversal symmetry of the inverse spin Hall effect voltage with respect to the heat gradient inversion.
The precise manipulation of transverse magnetic domain walls in finite/infinite nanowires with artificial defects under the influence of very short spin-polarized current pulses is investigated. We show that for a classical $3d$ ferromagnet material like Nickel, the exact positioning of the domain walls at room temperature is possible only for pulses with very short rise and fall time that move the domain wall reliably to nearest neighboring pinning position. The influence of the shape of the current pulse and of the transient effects on the phase diagram current-pulse length are discussed. We…
We present time-resolved measurements of the displacement of magnetic domain-walls (DWs) driven by vertical spin-polarized currents in track-shaped magnetic tunnel junctions. In these structures we observe very high DW velocities (600 m/s) at current densities below $10^7 A/cm^2$. We show that the efficient spin-transfer torque combined with a short propagation distance allows to avoid the Walker breakdown process, and achieve deterministic, reversible and fast ($\approx$ 1 ns) DW-mediated switching of magnetic tunnel junction elements, which is of great interest to the implementation of fast …
Friction plays an essential role in most physical processes that we experience in our everyday life. Examples range from our ability to walk or swim, to setting boundaries of speed and fuel efficiency of moving vehicles. In magnetic systems, the displacement of chiral domain walls (DW) and skyrmions (SK) by Spin Orbit Torques (SOT), is also prone to friction. Chiral damping, the dissipative counterpart of the Dzyaloshinskii Moriya Interaction (DMI), plays a central role in these dynamics. Despite experimental observation, and numerous theoretical studies confirming its existence, the influence…
Adiabatic spin transfer torque induced domain wall (DW) depinning from a notch and DW propagation in a nanowire with a series of notches is investigated. Surprisingly, notches help a current to depin a DW and make a DW easier to propagate along a wire. Following fascinating results on DW dynamics are found. 1) The depinning current density of a DW in a notch is substantially lower than the intrinsic threshold value below which a sustainable DW propagation doesn't exist in a homogeneous wire. 2) The DW displacement from a notch is insensitive to notch geometry and current density when it is bet…
A method for deterministic control of the magnetic order parameter using an electrical stimulus is highly desired for the new generation of spintronic and magnetoelectronic devices. Much effort has been focused on magnetic domain-wall motion manipulated by a successive injection of spin-polarized current into a magnetic nanostructure. However, an integrant high-threshold current density of 107~108 A/cm2 inhibits the integration of those nanostructures with low-energy-cost technology. In addition, a precise determination of the location of domain walls at nanoscale seems difficult in artificial…
We introduce a multiscale framework which combines time-dependent nonequilibrium Green function (TD-NEGF) algorithms, scaling linearly in the number of time steps and describing quantum-mechanically conduction electrons in the presence of time-dependent fields of arbitrary strength or frequency, with classical time evolution of localized magnetic moments described by the Landau-Lifshitz-Gilbert (LLG) equation. The TD-NEGF+LLG framework can be applied to a variety of problems where current-driven spin torque induces dynamics of magnetic moments as the key resource for next generation spintronic…
