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Understanding and controlling domain wall stochasticity in magnetic nanowires for spintronic application, Khalid Omari

09/01/2018 - Salle S208

Khalid Omari

Physics Department, University of Manchester, Manchester - UK

Spintronics has emerged as a “beyond-CMOS” promising field where electron spin is utilized to store/processes information in nanomagnetic materials with defined magnetic states. In ferromagnetic nanowires with in-plane-magnetisation there exist two bi-stable magnetic states that can be switched interchangeably by the injection and propagation of domain walls (DWs). In “thick” nanowires (t > 10 nm) DWs can be thought of as quasi-particles with internal vortex-like spin structure that propagate under the application of a magnetic field. Above a critical field (Walker-Breakdown field) DWs undergo complex transformations resulting in dynamical stochastic motion leading to stochastic switching. Such undeterministic switching behaviour resembles a critical challenge for realising spintronic devices.

In this talk, I present an experimental study supported by a novel micro-magnetic modelling approach that shows how proper choice of nanowire geometry and pinning site can result in controlling and in some cases complete suppression of switching stochasticity for vortex DWs pinning/depinning in permalloy nanowires. Moreover, I present a study on how different DW injection mechanisms (nucleation pad vs orthogonal current pulse line) can affect dynamic stochasticity [1].

In another interesting aspect of the talk I present a conceptual model of a full spintronic logic architecture where DW spin structure can be used to processes binary information in an interconnected network of magnetic nanowires [2,3].

Finally I give a brief insight into the first demonstration of a 1D hBN encapsulated-graphene spin-valve structure emerging from the novel new field of “Graphene Spintronics”.

[1] Hayward, T. & Omari, K. Beyond the quasi-particle : stochastic domain wall dynamics in soft ferromagnetic nanowires. Journal of Physics D : Applied Physics 50, 084006 (2017).

[2] Omari, K. et al. Ballistic rectification of vortex domain wall chirality at nanowire corners. Applied Physics Letters 107, 222403 (2015).

[3] Omari, K. & Hayward, T. Chirality-based vortex domain-wall logic gates. Physical Review Applied 2, 044001 (2014).