Theory of Current-Driven Domain Wall Motion: Spin Transfer versus Momentum Transfer

Tatara, Gen; Kohno, Hiroshi

doi:10.1103/physrevlett.92.086601

Cited by 885 publications

(458 citation statements)

References 27 publications

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“…The narrow (few nanometres wide) DWs in nanowires with very large PMA are the reason for their high sensitivity to spin-polarized currents [30]. But there is still a debate in the theoretical description of current-induced DW motion on how to describe the damping and whether there is an additional torque in the direction of the non-adiabatic torque [44,48], which arises from the same processes that contribute to magnetic damping. Such a torque, while it is not related to a true non-adiabatic torque, is still sometimes called a non-adiabatic torque.…”

Section: Underlying Theorymentioning

confidence: 99%

Nanowire spintronics for storage class memories and logic

Hrkac

Dean

Allwood

2011

Phil. Trans. R. Soc. A.

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Patterned magnetic nanowires are extremely well suited for data storage and logic devices. They offer non-volatile storage, fast switching times, efficient operation and a bistable magnetic configuration that are convenient for representing digital information. Key to this is the high level of control that is possible over the position and behaviour of domain walls (DWs) in magnetic nanowires. Magnetic random access memory based on the propagation of DWs in nanowires has been released commercially, while more dynamic shift register memory and logic circuits have been demonstrated. Here, we discuss the present standing of this technology as well as reviewing some of the basic DW effects that have been observed and the underlying physics of DW motion. We also discuss the future direction of magnetic nanowire technology to look at possible developments, hurdles to overcome and what nanowire devices may appear in the future, both in classical information technology and beyond into quantum computation and biology.

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Section: Underlying Theorymentioning

confidence: 99%

Nanowire spintronics for storage class memories and logic

Hrkac

Dean

Allwood

2011

Phil. Trans. R. Soc. A.

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“…However, the Joule heating has been a serious issue because a large current density j is necessary to overcome the pinning, and, therefore, the experiments usually have been done using a short pulse of electric current. The current-velocity relation of the domain-wall motion has been well studied [3][4][5][6][7][8][9] , which is sensitive to the impurity pinning, the Gilbert damping, and nonadiabatic effects.…”

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confidence: 99%

Universal current-velocity relation of skyrmion motion in chiral magnets

2013

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Current-driven motion of the magnetic domain wall in ferromagnets is attracting intense attention because of potential applications such as racetrack memory. There, the critical current density to drive the motion is B10 9 -10 12 A m À 2 . The skyrmions recently discovered in chiral magnets have much smaller critical current density of B10 5 -10 6 A m À 2 , but the microscopic mechanism is not yet explored. Here we present a numerical simulation of Landau-Lifshitz-Gilbert equation, which reveals a remarkably robust and universal currentvelocity relation of the skyrmion motion driven by the spin-transfer-torque unaffected by either impurities or nonadiabatic effect in sharp contrast to the case of domain wall or spin helix. Simulation results are analysed using a theory based on Thiele's equation, and it is concluded that this behaviour is due to the Magnus force and flexible shape-deformation of individual skyrmions and skyrmion crystal, which enable them to avoid pinning centres.

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“…Depending on the driving force, conventionally magnetic field and, more recently, spin-polarized current [4][5][6][7][8][9][10][11][12][13] , the propagation of DWs changes from a simple translation to more complex precessional modes 14 . Experimentally, indirect evidence of this transition is found from a sudden drop in the wall's velocity [15][16][17][18] , but direct observation of the precessional modes is lacking.…”

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confidence: 99%

Direct observation of the coherent precession of magnetic domain walls propagating along permalloy nanowires

et al. 2006

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The dynamics of the motion of domain walls (DWs) in magnetic materials has been extensively explored theoretically 1-3 . Depending on the driving force, conventionally magnetic field and, more recently, spin-polarized current 4-13 , the propagation of DWs changes from a simple translation to more complex precessional modes 14 . Experimentally, indirect evidence of this transition is found from a sudden drop in the wall's velocity [15][16][17][18] , but direct observation of the precessional modes is lacking. Here we show experimentally, using a combination of quasi-static and real-time measurement techniques, that DWs propagate along permalloy nanowires with a periodic variation in the chirality of the walls. The frequency of this oscillation is consistent with a precession of the propagating DW, increasing linearly with field according to the Larmor precession frequency. Current in the nanowire, large enough to significantly influence the DW velocity 18,19 , has little effect on the precession frequency but can be used to adjust the phase of the wall's precession. The highly coherent and reproducible motion of the DW revealed by our studies demonstrates that the DW is a well-defined macroscopic object whose phase is inextricably interlinked to the distance travelled by the DW.With the advent of magnetic nanowires of dimensions comparable to magnetic DW widths, it is possible to imagine that DWs propagating along such wires will exhibit a well-defined precessional mode due to confinement. In contrast, in extended structures, which have been extensively studied in the past, many modes are accessible 1,20 . Permalloy nanowires are attractive because they exhibit large anisotropic magnetoresistance (AMR) so that transverse and vortex walls can be readily detected and identified by resistance measurements. Furthermore, by breaking the onedimensional symmetry of the nanowire with a notch along one of its edges, the chirality of the DW can also be discerned 21 . Here, notched nanowires are used to directly show that the chirality of transverse DWs periodically reverses as the walls propagate in the precessional regime. This precessional motion is also detected in real time using time-resolved resistance measurements, which show that the precessional motion is, surprisingly, highly coherent.A scanning electron microscopy image of a typical permalloy nanowire with two contact lines, labelled A and B, is shown in Fig. 1a. Using a suitable field sequence (see the Methods section), a DW is introduced into section A-B of the nanowire by injecting a voltage pulse into contact line A. A magnetic field, H, is applied along the wire during the voltage pulse injection to assist the subsequent propagation of a DW. A fraction of the injected voltage pulse flows into section A-B, thereby injecting current into the nanowire as the DW propagates along it. The current density that flows into the nanowire scales as ∼0.5 × 10 8 A cm −2 V −1 . Positive current is defined as current flowing from line A to B.The existence of a DW in sectio...

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Theory of Current-Driven Domain Wall Motion: Spin Transfer versus Momentum Transfer

Cited by 885 publications

References 27 publications

Nanowire spintronics for storage class memories and logic

Nanowire spintronics for storage class memories and logic

Universal current-velocity relation of skyrmion motion in chiral magnets

Direct observation of the coherent precession of magnetic domain walls propagating along permalloy nanowires

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