Statics and field-driven dynamics of transverse domain walls in biaxial nanowires under uniform transverse magnetic fields

Lü, Jie

doi:10.1103/physrevb.93.224406

Cited by 21 publications

(25 citation statements)

References 67 publications

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“…which is the 1D self-adjoint Schrödinger operator appeared in previous works [32,33,37,38]. Then Eq.…”

Section: D-aemmentioning

confidence: 90%

Engineering Planar Transverse Domain Walls in Biaxial Magnetic Nanostrips by Tailoring Transverse Magnetic Fields with Uniform Orientation

Lü

2019

Nanomaterials

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Designing and realizing various magnetization textures in magnetic nanostructures are essential for developing novel magnetic nanodevices in the modern information industry. Among all these textures, planar transverse domain walls (pTDWs) are the simplest and the most basic, which make them popular in device physics. In this work, we report the engineering of pTDWs with arbitrary tilting attitude in biaxial magnetic nanostrips by transverse magnetic field profiles with uniform orientation but tuneable strength distribution. Both statics and axial-field-driven dynamics of these pTDWs are analytically investigated. It turns out that, for statics, these pTDWs are robust against disturbances which are not too abrupt, while for dynamics, it can be tailored to acquire higher velocity than Walker’s ansatz predicts. These results should provide inspiration for designing magnetic nanodevices with novel one-dimensional magnetization textures, such as 360° walls, or even two-dimensional ones, such as vortices and skyrmions.

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“…which is the 1D self-adjoint Schrödinger operator appeared in previous works [32,33,37,38]. Then Eq.…”

Section: D-aemmentioning

confidence: 90%

Engineering Planar Transverse Domain Walls in Biaxial Magnetic Nanostrips by Tailoring Transverse Magnetic Fields with Uniform Orientation

Lü

2019

Nanomaterials

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“…However the calculation process is hopelessly complicated. Inspired by the asymptotic approach [81][82][83][84][85] which is complicated due to the coexistence of H FL , H ADL and D.…”

Section: Mobility Change In Pma Systemsmentioning

confidence: 99%

Understanding current-driven dynamics of magnetic Néel walls in heavy metal/ferromagnetic metal/oxide trilayers

Wang

Lü

2019

New J. Phys.

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We consider analytically current-driven dynamics of magnetic Néel walls in heavy metal/ ferromagnetic metal/oxide trilayers where strong spin-orbit coupling and interfacial Dzyaloshinskii-Moriya interaction (i-DMI) coexist. We show that field-like spin-orbit torque (FL-SOT) with effective field along´n J(n being the interface normal andĴ being the charge current direction) and i-DMI induced torque can both lead to Walker breakdown suppression meanwhile leaving the wall mobility (velocity versus current density) unchanged. However, i-DMI itself can not induce the 'universal absence of Walker breakdown' (UAWB) while FL-SOT exceeding a certain threshold can. Finitelyenlarged Walker limits before UAWB are theoretically calculated and well explain existing data. In addition, change in wall mobility and even its sign-inversion can be understood only if the antidamping-like SOT is appended. For Néel walls in ferromagnetic-metal layer with both perpendicular and in-plane anisotropies, we have calculated the respective modifications of wall mobility under the coexistence of spin-transfer torque, SOTs and i-DMI. Analytics shows that in trilayers with perpendicular anisotropy strong enough spin Hall angle and appropriate sign of i-DMI parameter can lead to sign-inversion in wall mobility even under small enough current density, while in those with in-plane anisotropy this only occurs for current density in a specific range.Over the past decade, in heavy metal/ferromagnetic metal/oxide (HM/FMM/Oxide) trilayers, axial domain wall propagation in FMM layer with perpendicular magnetic anisotropy (PMA) or in-plane magnetic anisotropy (IPMA) driven by axial currents are experimentally observed [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41]. In certain case (Pt Co AlO x ), walls can move at a high velocity up to 400 m s -1 when current density is around -10 A cm 8 2 [37]. More interestingly, walls with certain polarity can even move in the direction of charge current [33][34][35][36][37][38][39][40][41], which is also confirmed by numerical simulations [42][43][44][45]. To understand these findings, spin-orbit torques (SOTs) from strong spin-orbit coupling (SOC) in these trilayers are proposed [46][47][48][49][50][51][52][53][54][55][56][57][58][59]. SupposeĴ is the charge current direction and n is interface normal. Mathematically, SOTs can be decomposed into two perpendicular components: (a) µ´(ˆ) m J n which is odd in magnetization direction m and usually referred to as field-like (FL) torque; (b) µ´´[ (ˆ)] m m J n which is even in m and usually called anti-damping-like (ADL) torque. Physically, two typical mechanisms are of most importance: the 'spin Hall torques' from the spin Hall effect (SHE) [60] in HM layer and the 'Rashba torques' from the structure inversion asymmetry (SIA) at the HM/ FMM interface. In early literatures, ADL-SOTs are believed to stem mostly from bulk SHE while field-like spinorbit torques (FL-SOTs) are mainly attributed to interfacial Rashba SOC. However, recent works based on scatt...

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“…To manipulate the TDW tilting attitude, using a uniform transverse magnetic field (TMF) is the easiest way and has been intensively studied 17 18 19 20 21 . However, a uniform TMF have two influences.…”

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confidence: 99%

“…First it pulls the magnetization out of the wire axis in the two domains and thus the TDW is not a 180° wall any more. Second, it induces a twisting in TDW azimuthal distribution 21 . For application in high-density NW devices, it is preferable to erase the twisting so as to minimize magnetization frustrations and stochastic fields.…”

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General planar transverse domain walls realized by optimized transverse magnetic field pulses in magnetic biaxial nanowires

Li¹,

Wang²,

Lü³

2017

Sci Rep

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The statics and field-driven dynamics of transverse domain walls (TDWs) in magnetic nanowires (NWs) have attracted continuous interests because of their theoretical significance and application potential in future magnetic logic and memory devices. Recent results demonstrate that uniform transverse magnetic fields (TMFs) can greatly enhance the wall velocity, meantime leave a twisting in the TDW azimuthal distribution. For application in high-density NW devices, it is preferable to erase the twisting so as to minimize magnetization frustrations. Here we report the realization of a completely planar TDW with arbitrary tilting attitude in a magnetic biaxial NW under a TMF pulse with fixed strength and well-designed orientation profile. We smooth any twisting in the TDW azimuthal plane thus completely decouple the polar and azimuthal degrees of freedom. The analytical differential equation describing the polar angle distribution is derived and the resulting solution is not the Walker-ansatz form. With this TMF pulse comoving, the field-driven dynamics of the planar TDW is investigated with the help of the asymptotic expansion method. It turns out the comoving TMF pulse increases the wall velocity under the same axial driving field. These results will help to design a series of modern magnetic devices based on planar TDWs.

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Statics and field-driven dynamics of transverse domain walls in biaxial nanowires under uniform transverse magnetic fields

Cited by 21 publications

References 67 publications

Engineering Planar Transverse Domain Walls in Biaxial Magnetic Nanostrips by Tailoring Transverse Magnetic Fields with Uniform Orientation

Engineering Planar Transverse Domain Walls in Biaxial Magnetic Nanostrips by Tailoring Transverse Magnetic Fields with Uniform Orientation

Understanding current-driven dynamics of magnetic Néel walls in heavy metal/ferromagnetic metal/oxide trilayers

General planar transverse domain walls realized by optimized transverse magnetic field pulses in magnetic biaxial nanowires

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