Magnetic skyrmions, which are topological swirling spin textures, have drawn much attention in spintronics because of their use as an information carrier with distinct robustness rooted in their topological nature. Real-time generation of skyrmions is therefore imperative for realizing skyrmion-based spintronic devices. However, to date, experimental demonstration has been limited to exquisite works with well-tuned samples. Here, we report a method to generate skyrmions by driving the stripe instability via an in-plane magnetic field. We have demonstrated that the key parameter determining the stripe domain instability is the stripe width, regardless of other material parameters. This skyrmion generation method can be applicable to generic magnetic films with perpendicular magnetic anisotropy. Our work will facilitate the development of skyrmion-based devices by offering a general method for controlling a large skyrmion population.

Steam generation by eco-friendly solar energy has immense potential in terms of lowcost power generation, desalination, sanitization, and wastewater treatment. Herein, highly efficient steam generation in a bilayer solar steam generator (BSSG) is demonstrated, which is comprised of a large-area SnSe−SnSe 2 layer deposited on a glassy carbon foam (CF). Both CF and SnSe−SnSe 2 possess high photothermal conversion capabilities and low thermal conductivities. The combined bilayer system cumulatively converts input solar light into heat through phonon-assisted transitions in the indirect band gap SnSe−SnSe 2 layer, together with trapping of sunlight via multiple scattering due to the porous morphology of the CF. This synergistic effect leads to efficient broadband solar absorption. Moreover, the low out-of-plane thermal conductivities of SnSe−SnSe 2 and CF confine the generated heat at the evaporation surface, resulting in a significant reduction of heat losses. Additionally, the hydrophilic nature of the acid-treated CF offers effective water transport via capillary action, required for efficient solar steam generation in a floating form. A high evaporation rate (1.28 kg m −2 h −1 ) and efficiency (84.1%) are acquired under 1 sun irradiation. The BSSG system shows high recyclability, stability, and durability under repeated steam-generation cycles, which renders its practical device applications possible.

which information is encoded by magnetic skyrmions in a magnetic wire structure. Skyrmion racetrack memory has been considered as an appealing alternative to next-generation memory technology because of its small skyrmion size, highspeed operation, and stability. [8][9][10] The minimum size of skyrmion can be smaller than that of the magnetic domain wall, [11] where the minimum size determines the maximized device density. In addition, based on additional topological stability, the critical depinning current density in the skyrmion racetrack memory device is four orders of magnitude lower than that in the domain-wall racetrack memory. Skyrmion racetrack memory requires the sequential operation of electrical generation, deletion, and shifting of individual skyrmions in a single racetrack device. [12] Hence, the realization of skyrmion racetrack memory has been considered to be a challenging issue, and the feasibilities of the three main operations of generation/ deletion/shift have typically been demonstrated individually. Specifically, since the experimental observations of magnetic skyrmions at room temperature, [13,14] various approaches have been proposed for skyrmion generation using magnetic fields, [13,15,16] current-induced spin torque, [14,[17][18][19][20] voltagecontrolled magnetic anisotropy, [21] and thermal energy. [22,23] The deletion and shift of skyrmions have been successively achieved by current-induced spin-orbit torque (SOT). [13,[16][17][18][19][20] In the manipulation of skyrmions, the inevitable skyrmion Hall effect, which must be removed for skyrmion racetrack application, has also been experimentally observed, [24,25] but can be suppressed using ferrimagnetic or synthetic antiferromagnetic systems. [26] At this stage, the remaining experimental challenge toward achieving skyrmion racetrack memory is the implementation of all these three operations within a single device. Büttner et al. [17] reported the two operations of generating and shifting skyrmion in one device using a tailored pinning site, whereas Woo et al. [18] achieved the electrical generation and deletion of a single skyrmion in one device using device-compatible geometry. In addition, Yu et al. [27] realized a skyrmion shift device using writing and shifting skyrmions in one device. However, whether all three operations of generation/deletion/shift can be realized on a single device has not been experimentally proven. Here, we introduce a practical method for generating and deleting isolated skyrmions via vertical current injection.The magnetic skyrmion is a topologically protected spin texture that has attracted much attention as a promising information carrier because of its distinct features of suitability for high-density storage, low power consumption, and stability. One of the skyrmion devices proposed so far is the skyrmion racetrack memory, which is the skyrmion version of the domain-wall racetrack memory. For application in devices, skyrmion racetrack memory requires electrical generation, deletion, and displacement ...

Efficient current‐induced switching of perpendicular magnetization is an essential task in spintronics for realizing high‐performance information processing and for storage device application. However, the spin‐orbit torque (SOT) by injection of in‐plane polarized spins cannot deterministically switch the magnetization of ferromagnetic thin films with perpendicular magnetic anisotropy (PMA) without an additionally applied in‐plane external magnetic field to break the symmetry of the PMA. Considering the difficulties of applying the magnetic field to the localized area only within a device structure, it is essential to contrive a facile field‐free SOT switching mechanism. Here, deterministic field‐free SOT switching of perpendicular magnetization is achieved in amorphous and ferrimagnetic Gd/Co multilayers accompanied by a tilted magnetic anisotropy axis. This tilted anisotropy originates from the combined contributions of many internal anisotropies in different orientations from the multilayers and is shown to be controllable. It is expected that the introduction of controlled tilted anisotropy into Gd/Co multilayers over the entire film surface in the present study can be extended to the development of wafer‐scale technologies for the spintronics memory and logic devices.