Magnetic skyrmions are topologically nontrivial spin textures with envisioned applications in energy-efficient magnetic information storage. Toggling the presence of magnetic skyrmions via writing/deleting processes is essential for spintronics applications, which usually require the use of a magnetic field, a gate voltage or an electric current. In a study just published in Nature Communications, a group of researchers led by Foundry users Dr. Gong Chen and Prof. Kai Liu at Georgetown University have demonstrated a new, field-free method to reversibly write/delete skyrmions at room temperature via hydrogen chemisorption/desorption on the surface of magnetic thin films.
Using the Foundry’s spin-polarized low-energy electron microscope (SPLEEM), the researchers have observed skyrmion creation and annihilation during hydrogen chemisorption/desorption cycles. They find that the adsorption of less than one atomic layer of hydrogen on the surface of Ni/Co/Pd/W(110) multilayers changes the balance of magnetic energy contributions, particularly the magnetic anisotropy, which in turn drives the skyrmion creation/annihilation as the energy landscape evolves.
Using the SPLEEM for magnetization vector mapping, Chen has resolved the spin structure of the written skyrmions and shown that they are left-handed hedgehog Néel-type. Monte-Carlo simulations support the interpretation attributing the reversible skyrmion writing and deleting to anisotropy changes. The roles of hydrogen and oxygen on magnetic anisotropy and skyrmion deletion on other magnetic surfaces are also demonstrated.
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Such ambient temperature reversible skyrmion operations in the absence of magnetic field, gate voltage or electric current provide new paths for the design of skyrmion-based spintronics. It adds a new degree of freedom to the emerging field of chiral spintronics, where spin textures may be controlled in a tunable and contactless way, without the need for electrical leads. This may be particularly relevant for three-dimensional information storage schemes involving complex architectures and large numbers of skyrmions, such as racetrack memories. This effect can also be readily integrated into magneto-ionic devices, where the adsorption/desorption takes place at buried interfaces. Such skyrmion-based devices with magneto-ionic functionality may be used for magnetic memory and logic devices, as well as artificial synapses.
Foundry research was supported by Staff Scientists Colin Ophus and Andreas Schmid. Other researchers involved include Alberto Quintana of Georgetown University, Heeyoung Kwon of the Korea Institute of Science and Technology, Changyeon Won of Kyung Hee University, Haifeng Ding of Nanjing University, and Yizheng Wu of Fudan University.
This article has been adapted from an existing Georgetown University press release.