Three-dimensional nanomagnetism
Controlling magnetic materials on the nanoscale plays a key role in our society, having enabled for instance the development of thin film hard disk media, which has brought our ability to store and share information to unprecedented levels. Today, beyond hard disks, nanomagnetism offers key advantages over alternative technological approaches, including intrinsic non-volatility and very low power consumption, with devices such as Magnetic Random-Access Memory (MRAM) close to largescale production.
Within this field, most magnetic nanostructures are intrinsically 2D in nature, in part due to continued exploitation of sophisticated (2D) thin film processing techniques. While planar geometries have given rise to a multitude of functionalities and devices, it is now becoming apparent that to address the fundamental bottlenecks faced by current technologies, a paradigm shift is required.
A radically-new approach to overcome current fundamental limits, consisting of moving to more complex, hierarchical systems that exploit three-dimensional (3D) magnetic configurations and geometries. 3D nanoscale magnetic phenomena broadly open up a range of strategies for enhancing computation, sensing and communication technologies. For example, the increased complexity within 3D interacting magnetic networks offers the opportunity for increased complexity in neuromorphic computation analogues, while the massive degeneracy in reconfigurable 3D artificial magnetic crystals offers new prospects in spin-wave logic and communication devices.
Beyond a device perspective, wholly new physics are predicted to emerge in 3D. This includes new magneto-chiral effects in curved geometries, novel spin configurations, ultra-fast motion of spin textures, novel interplay mechanisms between spatial and spin topologies, and strong coupling between magnetism and temperature or strain, to cite a few.
Our group is developing a cutting-edge research program on 3D nanomagnetism, having reported some of the most advanced experimental works in 3D nanomagnetism to date. This includes multiple areas, including 3D nanofabrication, magneto-optics, X-ray microscopy and new effects in multi-layered systems. The main research areas in which I am currently working, and key publications related to them, are explained below.
Main research lines
3D printing at the nanoscale
We are pioneering new nanofabrication methods based on focused electron and ion beams for the advanced 3D printing of magnetic nanostructures. We have exploited this technique to realise the smallest magnetic Möbius strip ever realised, and to move domain walls in nanowire 3D conduit devices for the first time, using external magnetic fields.
Key publications:
Skoric et al, Nano Letters 20, 184 (2020).
Fernández-Pacheco et al, Sci. Rep 3, 1492 (2013).
Fernández-Pacheco, J. Phys. D 42, 055005 (2009).
3D magneto-optics & spintronics
We are developing new optical methods such as the "Dark-Field magneto-optical Kerr effect", for the advanced characterization of 3D magnetic nanostructures. This new technique allows us to probe the magnetic state of nanomagnets with complex 3D geometries with great sensitivity and spatial resolution. We combine this technique with magnetoelectrical measurements for the advanced characterisation of 3D spintronic devices.
Key publications:
Skoric et al, ACS Nano, 10.1021/acsnano.1c10345
Meng et al, ACS Nano 15, 4, 6765 (2020).
Sanz-Hernández et al, ACS Nano 11, 11066 (2017).
3D effects in multilayered thin film heterostructures
We investigate new forms of coupling between magnetic layers in multilayered heterostructures for applications in 3D spintronics. We have observed new forms of chiral spin states between layers due to the interlayer DMI, and during my time at the group of Prof. Cowburn in Cambridge, we stabilised and propagated topological solitons in multilayers exploiting RKKY and anisotropy energies.
Key publications:
Fernández-Pacheco et al, Nature Materials 18, 679 (2019).
Fernández-Pacheco et al, Adv. Interf. Materials 3, 1600097 (2016).
Lavrisjen et al, Nature 493, 647(2013).
Fernández-Pacheco et al, Phys. Rev. B 86, 104422 (2012).
Geometrical control of topological spin textures & defects
We are exploring new magnetic effects at the nanoscale by coupling complex 3D geometries and spin states. We have for instance demonstrated how "DNA-like" nanomagnetic double helices can be exploited to imprint chiral spin textures and topological defects in 3D nanostructures.
Key publications:
Sanz-Hernández et al, ACS Nano 14, 8084 (2020).
Donnelly et al, Nature Nanotechnology 17, 136 (2022)
For an overview of our recent research on 3D nanomagnetism, watch some of our recent online talks