Perspectives on 3D spintronics

Time: Friday, October 12th, 10:10
Speaker: Amalio FERNANDEZ-PACHECO, University of Cambridge

Three-dimensional nanomagnetism is a new and exciting area of research focused on investigating nanomagnets that extend beyond the standard planar configuration [1]. In these systems, with unconventional geometries and spin interactions, new physical effects emerge, with geometry, topology and chirality becoming interlinked, which paves the way to novel devices with functionalities beyond the substrate plane. Specifically, future non-volatile 3D devices are expected to have ultra-high storage densities and very high interconnectivity, of great interest for future neuromorphic computing devices [2].
The leap to 3D is extremely complex from a fabrication and characterisation point of view, but it is starting to become possible thanks to new nanotechnology tools suitable to create and probe 3D geometries and spin configurations [3]. In this talk, I will review the state of the art of 3D nanomagnetism and will present some of our recent work on 3D magnetic nanostructures for applications in spintronics.
The introduction of novel 3D nano-printing methods based on focused electron beams is allowing us for the first time to prototype complex 3D nanomagnets [4-6]. In particular, the exploitation of auto-catalytic effects can be used to create diameter-modulated suspended nanowires [7], where advanced X-ray magnetic microscopy experiments reveal the presence of skyrmionic tubes during their magnetic reversal, in agreement with recent theoretical predictions [8]. Additionally, we have successfully injected domain walls from the substrate plane onto 3D Permalloy “ramped” nanowires interconnected to the substrate [9], a pioneering work comprising the development of a new 3D magneto-optical nano-magnetometry method exploiting dark-field effects. This work opens an exciting new route to advanced operation of 3D domain wall conduits.
I acknowledge funding from EPSRC grants EP/M008517/1 and EP/L015978/1, from the Cambridge Winton Program for the Physics of Sustainability, the Royal Society and EU funding via the COST action CELINA.
[1] Fernández-Pacheco et al, Nature Comm. 8, 15756 (2017).
[2] Torrejón et al, Nature 547, 428 (2017).
[3] Donnelly et al, Nature 547, 328 (2017).
[4] Sanz-Hernández et al, Beilstein J. Nanotechnol. 8, 2151 (2017).
[5] Fowlkes et al, ACS Appl. Nano Mater. 1, 1028 (2018).
[6] Sanz-Hernández et al, Nanomaterials 8, 483 (2018).
[7] Pablo-Navarro et al. J. Phys. D: Appl. Physics 50, 18LT01 (2017).
[8] Charilaou et al, arXiv:1711.03511 (2017).
[9] Sanz-Hernández et al, ACS Nano 11, 11066 (2017).

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