Yu Li's page

Synthetic ferromagnets (SFMs) possess the same layer structure found in the widely studied synthetic antiferromagnets. This consists of two ferromagnetic (FM) layers separated by a non-magnetic (NM) spacer forming the structure FM1/NM/FM2, but SFMs describe the case where the interlayer exchange coupling promotes the parallel alignment of the magnetizations of the FM layers. The frequency and phase of the dynamic response of these structures depends sensitively on the interlayer exchange coupling as well as on the individual layer magnetizations. Through experiments and numerical simulations, we show that the dynamic response of the two ferromagnetic layers has an orthogonal dependence on the difference in layer magnetization and interlayer coupling allowing both parameters to be determined accurately …

(Abstract) The topological properties of skyrmionic quasiparticles such as magnetic skyrmions and skyrmioniums enable their applications in future low-power, ultradense nanocomputing and neuromorphic systems. We propose here an all-magnetic skyrmionic interconnect, which has so far been the “missing component.” This interconnect will…

We developed a surface roughness model for magnetic systems, by taking into account the space-dependent uniaxial anisotropy and Dzyaloshinskii-Moriya interaction (DMI). The spacial variation is determined by the surface topography of multilayer structure, which is characterised by atomic force microscopy. By using micromagnetic technique, we found that the DMI is required for the stabilisation of meron-like spin textures in an in-plane magnetised [Pt/Co/Ta] trilayer structure. Furthermore, with the presence of surface roughness, much larger textures can be stabilised with lateral dimensions from 0.2 to 2 μm, in agreement with experimental observations. Please find more out in our published paper!

The image is captured during the field-induced magnetic transition of a skyrmion lattice in theory. The colour code indicates the component of magnetisation perpendicular to the film surface. Increasing of the magnetic field forces skyrmion diameter to expand. Then the lattice inversion occurs involving the breaking of domain alls accompained with the emergence of transient antiskyrmions.

Our recent theoretical paper on “Tunable terahertz oscillation arising from Bloch-point dynamics in chiral magnets” has now been published at Physical Review Research. This work arose from a collaboration between the University of Manchester(NEST group, Skyrmionics group, and Theoretical physics group) with the ETH Zürich (Metal Physics and Technology group). It reveals that the formation/annihilation of skyrmions will give rise to an emergent electric field with the frequency in the THz regime. The electric signal is due to the ultra-fast Bloch-point propagation, and both the amplitude and frequency can be tuned by the manipulation of Bloch-point dynamics. Our studies provide a concept of directly exploiting topological singularities which may be relevant for THz skyrmion-based electronic devices …

Magnetic skyrmions have attracted considerable interest, especially after their recent experimental demonstration at room temperature in multilayers. The robustness, nanoscale size and non-volatility of skyrmions have triggered a substantial amount of research on skyrmion-based low-power, ultra-dense nanocomputing and neuromorphic systems such as artificial synapses. Room-temperature operation is required to integrate skyrmionic synapses in practical future devices. Here, we numerically propose a nanoscale skyrmionic synapse composed of magnetic multilayers that …

I was really excited to attend the British-German WE-Heraeus-Seminar held in Physikzentrum Bad Honnef, Germany (1st - 5th Dec., 2019). The topic this year is „Skyrmions in Magnetic Materials“.

In the poster session, I was honored to present our recent work: „Tuneable Bloch-point dynamics during switching of skyrmions and antiskyrmions in chiral magnets” (manuscript available on arXiv), and I also won the best poster prize!

Skyrmionic textures are being extensively investigated, due to the occurrence of novel topological magnetic phenomena and their promising applications in a new generation of spintronic devices. In this work, our considerations go beyond static skyrmions and …

Really excited to participate the 12th International Symposium on Hysteresis Modeling and Micromagnetics (HMM2019) in Crete, Greece (19th-22nd May, 2019). I presented a talk in the first session “Magnetic Solitons I”, with the title “Controllable THz Bloch-point propagation in the switching process of magnetic skyrmions“. I also presented a poster from our recently published work Collective antiskyrmion-mediated phase transition and defect-induced melting in chiral magnetic films.

Magnetic phase transitions are a manifestation of competing interactions whose behavior is critically modified by defects and becomes even more complex when topological constraints are involved. In particular, the investigation of skyrmions and skyrmion lattices offers insight into fundamental processes of topological-charge creation and annihilation upon changing the magnetic state. Nonetheless …