Abstract:Dynamics of multiple transverse walls (TWs) in a magnetic nanostripe is studied by micromagnetic simulations. It shows that, when TWs are arranged in a stripe with same orientation, they will attract each other and finally annihilate. However, when adjacent TWs are arranged with opposite orientation, a metastable complex wall can be formed, e.g., two TWs lead to 360o wall. For three or more TWs, the formed complex wall includes a number of 360o substructures, which is called multiple 360o structure (M360S) her… Show more
“…As u further increases, TDW would turn into a vortex wall, and one can observes the rapid increment of 〈 v 〉 for the vortex wall. Another distinction is u c is significantly smaller than the benchmark u w , which has also been reported before 18 , 26 , 33 . Figure 2 Average velocity 〈 v 〉 of TDW and 360DW as a function of spin current velocity u with different in-plane biaxial anisotropy (solid symbols), where K x = K y and K z = 0 have been set.…”
Section: Resultssupporting
confidence: 62%
“…However, for a driven current larger than a critical value, TDW motion would suffer from Walker breakdown 12 – 14 . Recently, 360° domain wall (360DW), which is formed by the combination of two TDWs with opposite orientations, has attracted much attention 15 – 33 . One of the advantages is that 360DW shows much weaker stray field as compared to TDW, allowing more stable packing density 27 .…”
Section: Introductionmentioning
confidence: 99%
“…The field- and current-driven behaviors of 360DW also differ qualitatively from those of TDW 18 . For example, 360DW may move along a magnetic stripe like TDW under a small driven current, but it will annihilate when the driven current is above a critical value u c 18 , 26 , 33 . These characteristics may lead to interesting applications to DW devices 16 , 18 , 20 , 24 , 25 , and may be also more suitable for building racetrack memory 27 , 28 , 30 , 32 .…”
Section: Introductionmentioning
confidence: 99%
“…On one side, 360DW is created from two transverse 180DWs, which have opposite topological charges. It is then stabilized through a balance between exchange and demagnetization energies, however, the stability of which may be broken by increasing of out-of-plane magnetic moment generated by fast domain-wall motion, where attractive demagnetization energies reduce accordingly 26 , 33 . On the other side, supposing magnetic moments are constrained in xy plane, then the degree of spin freedom is reduced to 1.…”
By micromagnetic simulations, we study the current-driven 360° domain wall (360DW) motion in ferromagnetic nanostripe with an in-plane biaxial anisotropy. We observe the critical annihilation current of 360° domain wall can be enhanced through such a type of anisotropy, the reason of which is the suppression of out-of-plane magnetic moments generated simultaneously with domain-wall motion. In details, We have found that the domain-wall width is only related to K
y − K
x, with K
x(y) the anisotropy constant in x(y) direction. Taking domain-wall width into consideration, a prior choice is to keep K
y ≈ K
x with large enough K. The mode of domain-wall motion has been investigated as well. The traveling-wave-motion region increases with K, while the average DW velocity is almost unchanged. Another noteworthy feature is that a Walker-breakdown-like motion exists before annihilation. In this region, though domain wall moves with an oscillating behavior, the average velocity does not reduce dramatically, but even rise again for a large K.
“…As u further increases, TDW would turn into a vortex wall, and one can observes the rapid increment of 〈 v 〉 for the vortex wall. Another distinction is u c is significantly smaller than the benchmark u w , which has also been reported before 18 , 26 , 33 . Figure 2 Average velocity 〈 v 〉 of TDW and 360DW as a function of spin current velocity u with different in-plane biaxial anisotropy (solid symbols), where K x = K y and K z = 0 have been set.…”
Section: Resultssupporting
confidence: 62%
“…However, for a driven current larger than a critical value, TDW motion would suffer from Walker breakdown 12 – 14 . Recently, 360° domain wall (360DW), which is formed by the combination of two TDWs with opposite orientations, has attracted much attention 15 – 33 . One of the advantages is that 360DW shows much weaker stray field as compared to TDW, allowing more stable packing density 27 .…”
Section: Introductionmentioning
confidence: 99%
“…The field- and current-driven behaviors of 360DW also differ qualitatively from those of TDW 18 . For example, 360DW may move along a magnetic stripe like TDW under a small driven current, but it will annihilate when the driven current is above a critical value u c 18 , 26 , 33 . These characteristics may lead to interesting applications to DW devices 16 , 18 , 20 , 24 , 25 , and may be also more suitable for building racetrack memory 27 , 28 , 30 , 32 .…”
Section: Introductionmentioning
confidence: 99%
“…On one side, 360DW is created from two transverse 180DWs, which have opposite topological charges. It is then stabilized through a balance between exchange and demagnetization energies, however, the stability of which may be broken by increasing of out-of-plane magnetic moment generated by fast domain-wall motion, where attractive demagnetization energies reduce accordingly 26 , 33 . On the other side, supposing magnetic moments are constrained in xy plane, then the degree of spin freedom is reduced to 1.…”
By micromagnetic simulations, we study the current-driven 360° domain wall (360DW) motion in ferromagnetic nanostripe with an in-plane biaxial anisotropy. We observe the critical annihilation current of 360° domain wall can be enhanced through such a type of anisotropy, the reason of which is the suppression of out-of-plane magnetic moments generated simultaneously with domain-wall motion. In details, We have found that the domain-wall width is only related to K
y − K
x, with K
x(y) the anisotropy constant in x(y) direction. Taking domain-wall width into consideration, a prior choice is to keep K
y ≈ K
x with large enough K. The mode of domain-wall motion has been investigated as well. The traveling-wave-motion region increases with K, while the average DW velocity is almost unchanged. Another noteworthy feature is that a Walker-breakdown-like motion exists before annihilation. In this region, though domain wall moves with an oscillating behavior, the average velocity does not reduce dramatically, but even rise again for a large K.
“…Additionally, we demonstrate an elegant extension of the injection technique to achieve the controlled motion of 360° DWs through nanowires. Spatial manipulation of 360° DWs is not possible using uniform global fields as opposite forces are generated on each composite magnetic charge 21 22 23 and current-driven motion requires high current densities 20 24 or multiple-wire geometries 25 as well as the incorporation of macroscopic electrodes within the device architecture. A tip-based technique for writing magnetic charge structures into continuous films has recently been described 26 , relying on a heated tip in conjunction with a complex multi-layered film and requiring a considerable applied global magnetic field to function.…”
Realising the promise of next-generation magnetic nanotechnologies is contingent on the development of novel methods for controlling magnetic states at the nanoscale. There is currently demand for simple and flexible techniques to access exotic magnetisation states without convoluted fabrication and application processes. 360° domain walls (metastable twists in magnetisation separating two domains with parallel magnetisation) are one such state, which is currently of great interest in data storage and magnonics. Here, we demonstrate a straightforward and powerful process whereby a moving magnetic charge, provided experimentally by a magnetic force microscope tip, can write and manipulate magnetic charge states in ferromagnetic nanowires. The method is applicable to a wide range of nanowire architectures with considerable benefits over existing techniques. We confirm the method’s efficacy via the injection and spatial manipulation of 360° domain walls in Py and Co nanowires. Experimental results are supported by micromagnetic simulations of the tip-nanowire interaction.
Soliton-based computing relies on their unique properties for transporting energy and emerging intact from head-on collisions. Magnetic domain walls are often referred to as solitons disregarding the strict mathematical definition requiring the above scattering property. Here we demonstrate the conditions of elastic and inelastic scattering for spin–orbit torque-induced dynamics of relativistic domain walls on the technologically relevant Mn$$_2$$
2
Au antiferromagnetic material. We show that even domain walls with opposite winding numbers can experience elastic scattering and we present the corresponding phase diagram as a function of the spin–orbit field strength and duration. The elastic collision requires minimum domain walls speed, which we explain assuming an attractive potential created by domain wall pair. On the contrary, when the domain walls move at lower speeds, their collision is inelastic and results in a dispersing breather. Our findings will be important for the development of soliton-based computing using antiferromagnetic spintronics and we discuss their prospects for building NOT and XOR gates.
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