Application concepts for ultrafast laser-induced skyrmion creation and annihilation

Abstract

Magnetic skyrmions can be created and annihilated in ferromagnetic multilayers using single femtosecond infrared laser pulses above a material-dependent fluence threshold. From the perspective of applications, optical control of skyrmions offers a route to a faster and, potentially, more energy-efficient new class of information-technology devices. Here, we investigate laser-induced skyrmion generation in two different materials, mapping out the dependence of the process on the applied field and the laser fluence. We observe that sample properties like strength of the Dzyaloshinskii–Moriya interaction and pinning do not considerably influence the initial step of optical creation. In contrast, the number of skyrmions created can be directly and robustly controlled via the applied field and the laser fluence. Based on our findings, we propose concepts for applications, such as all-optical writing and deletion, an ultrafast skyrmion reshuffling device for probabilistic computing, and a combined optical and spin–orbit torque-controlled racetrack.

Deterministic Generation and Guided Motion of Magnetic Skyrmions by Focused He$^+$-Ion Irradiation

“…In line with the modification of the hysteresis behavior for different irradiation doses, we reduced the magnetic field to a value for which spontaneous nucleation of stripe domains remains suppressed but skyrmion nucleation from an external stimulus is possible. 16,27 At the outset, we confirmed that our non-irradiated Pt/CoFeB/MgO multilayer supports skyrmion nucleation. As a reference for the unmodified magnetic film in Fig.…”

“…They finally appear randomly distributed inside the illuminated area of the magnetic film. 23,27 However, a controllable, reproducible and reliable localization of the skyrmion nucleation is often required -both for future applications in data technology 28,29 as well as for fundamental research, e.g., to realize repetitive pump-probe experiments on skyrmion dynamics. 18 Previous attempts to control the localization of skyrmions include structural patterning of the magnetic film with notches 16, 30,31 and discs 11 as well as the introduction of defects 32,33 and nano-pockets 34 to define positions for skyrmion nucleation.…”

“…The material system is well-known from previous experiments on skyrmion nucleation and supports both SOT-and laser-assisted nucleation. 16,23,27 He + -ion nanopatterning was carried out with a ZEISS Orion Nanofab. We locally irradiated the magnetic film with He + -ion doses between 25 and 400 ions/nm 2 in predefined patterns with a nominal resolution of 10 nm.…”

“…2b was not patterned into a racetrack and skyrmions form in the entire area illuminated by the laser where the laser fluence overcomes the nucleation threshold. 23,27 In samples with an ion irradiated 2D area covering half the racetrack (c) and with a 1D line pattern (d), we applied a single biploar current pulse to create skyrmions. To suppress nucleation in non-irradiated regions, we increased the applied field compared to the nucleation in non-irradiated racetracks.…”

Pinning and gyration dynamics of magnetic vortices revealed by correlative Lorentz and bright-field imaging

“…Due to their stability and unique topological properties, these textures have sparked ideas for a vast number of technological applications such as (racetrack) memories [7][8][9][10], logical-gates [11,12] and neuromorphic computing [13]. While various control schemes for the manipulation of these textures by means of external magnetic fields [14,15], electrical currents [16][17][18], or optical pulses [3,18,19] are widely established, studies probing their interaction with defects are still highly sought after.…”