Mechanism for domain wall pinning and potential landscape modification by artificially patterned traps in ferromagnetic nanowires

Petit, D.; Jausovec, Ana-Vanessa; Zeng, Huang; Lewis, E. R.; O’Brien, Liam; Read, Dan; Cowburn, R. P.

doi:10.1103/physrevb.79.214405

Cited by 66 publications

(43 citation statements)

References 30 publications

(25 reference statements)

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“…Figure 5d We now consider the pinning required to form energetically unfavourable monopoles. Domain-wall spectroscopy in permalloy nanowires demonstrated that remote magnetic charge provides effective domain-wall pinning 21 only out to 100 nm and revealed a local pinning potential well within the magnetic Coulomb barrier at an isolated permalloy Q = +1 T -vertex 22 . We conclude that local vertex effects dominate and the inset of Fig.…”

Section: (R Ijmentioning

confidence: 99%

Direct observation of magnetic monopole defects in an artificial spin-ice system

et al. 2010

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Free monopoles have fascinated and eluded researchers since their prediction by Dirac 1 in 1931. In spin ice, the bulk frustrated magnet, local ordering principles known as ice rules-two-in/two-out for four spins arranged in a tetrahedron-minimize magnetic charge. Remarkably, recent work 2-5 shows that mobile excitations, termed 'monopole defects', emerge when the ice rules break down 2 . Using a cobalt honeycomb nanostructure we study the two-dimensional planar analogue called kagome or artificial spin ice. Here we show direct images of kagome monopole defects and the flow of magnetic charge using magnetic force microscopy. We find the local magnetic charge distribution at each vertex of the honeycomb pins the magnetic charge carriers, and opposite charges hop in opposite directions in an applied field. The parameters that enter the problem of creating and imaging monopole defects can be mapped onto a simple model that requires only the ice-rule violation energy and distribution of switching fields of the individual bars of a cobalt honeycomb lattice. As we demonstrate, it is the exquisite interplay between these energy scales in the cobalt nanostructure that leads to our experimental observations.The dipolar interactions of a given spin with all of its nearest neighbours cannot be satisfied on a triangular lattice, resulting in a frustrated magnetic state with strong correlations and a local ordering principle, but no long-range order. Owing to its equivalence to the electrical charge distribution in water ice 6 , the materials are known as 'spin ices' and the local ordering scheme as the 'ice rules'. Spin-ice materials such as Dy 2 Ti 2 O 7 have been subject to an intense research effort 7,8 and frustrated magnetism has evolved into a deeply interdisciplinary field, providing model systems for complex biological problems and a mathematical basis for the neural network algorithm from the Sherrington-Kirkpatrick model 9 .A powerful way to understand spin ice is to consider the magnetic dipole as a positive and negative magnetic charge (±q) separated by one lattice spacing. The ice rule can then be described as the local minimization at each lattice site i of the total magnetic charge (Q i, = q i ). Predictions suggest that the magnetic properties can be fractionalized, with mobile excitations carrying magnetic charge, rather than spin, and their interactions being described by a magnetic Coulomb's law 2 (equation (1))where V 0 is the self-energy and r ij is the separation. Although these topological excitations are confined to the dipole lattice, and they are compatible with Maxwell's equations 10 , their free magnetic charge character has led to the nomenclature magnetic Blackett Laboratory, Imperial College, Prince Consort Road, London SW7 2AZ, UK. *e-mail: W.Branford@imperial.ac.uk.monopole defects. Recent studies 3-5,10 in rare-earth pyrochlores strongly suggest that monopole defects exist in bulk spin ice 10 .Creating an odd number of intersecting dipoles, as in 'kagome spin ice' 11 , is interesting becaus...

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Section: (R Ijmentioning

confidence: 99%

Direct observation of magnetic monopole defects in an artificial spin-ice system

et al. 2010

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“…10͒ and a T-shaped trap. 11 The two possible equilibrium pinned configurations for a head-to-head DW are shown in Fig. 1͑a͒: the trap acts either as a potential well or a potential barrier, depending on the orientation of the magnetization in the core of the DW, and the two equilibrium configurations can be clearly distinguished by measuring the depinning field.…”

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confidence: 99%

Kinetic depinning of a magnetic domain wall above the Walker field

Lewis

Petit

O’Brien

et al. 2011

Applied Physics Letters

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Domain wall propagation in micrometric wires: Limits of single domain wall regime J. Appl. Phys. 111, 07E311 (2012) Magnetic structure and resonance properties of a hexagonal lattice of antidots Low Temp. Phys. 38, 157 (2012) Thermally activated domain wall dynamics in a disordered magnetic nanostrip J. Appl. Phys. 109, 07D345 (2011) Noise investigation of the orthogonal fluxgate employing alternating direct current bias J. Appl. Phys. 109, 07E529 (2011) Comparison of electrical techniques for magnetization dynamics measurements in micro/nanoscale structures

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“…distinguishing narrow-P from wide-AP or wide-P from narrow-AP); the clear difference in magnitude between the parallel and antiparallel switching fields means that different chiralities can reliably be distinguished. Note that micromagnetic simulations 18 showed that in the narrow-AP case, the DW incident on the trap splits into two DWs; the second DW moves along the vertical arm and switches it. In the wide-AP case, the "transmission field" does not correspond to transmission of the DW past the trap, but instead to re-nucleation of a new domain next to the trap.…”

Section: Effect Of Not Gates On Dw Chirality: Testing For Chiralmentioning

confidence: 99%

“…These measurements were already carried out in Ref. 18, but for nanostrips of different dimensions, which were fabricated using focused ion beam patterning rather than electron beam lithography. We therefore fabricated additional structures with a trap only (no NOT gate) and measured the transmission field for each different DW-trap configuration.…”

Section: Effect Of Not Gates On Dw Chirality: Testing For Chiralmentioning

confidence: 99%

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Chirality dependence of nanoscale ferromagnetic NOT gates

Lewis

Petit

O’Brien

et al. 2011

Journal of Applied Physics

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The behavior of a transverse domain wall (DW) interacting with a ferromagnetic NOT gate is studied with specific emphasis on the role of the DW chirality (sense of rotation of magnetization crossing the DW). We examine both the effect of the incoming DW chirality on the operation of the NOT gate and the effect of the gate on the DW chirality. We find that the chirality of the incoming DW does not affect the range of fields over which the NOT gate operates correctly. The effect of the NOT gate on the DW chirality depends on the chirality of the incoming DW: when the DW is incident on the NOT gate with the wide side of the DW on the inside of the V-shape formed by the gate, the chirality is conserved, but when the DW is incident on the gate with its wide side on the outside of the V-shape, the chirality may reverse.

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Mechanism for domain wall pinning and potential landscape modification by artificially patterned traps in ferromagnetic nanowires

Cited by 66 publications

References 30 publications

Direct observation of magnetic monopole defects in an artificial spin-ice system

Direct observation of magnetic monopole defects in an artificial spin-ice system

Kinetic depinning of a magnetic domain wall above the Walker field

Chirality dependence of nanoscale ferromagnetic NOT gates

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