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Magnetic materials offer an opportunity to overcome the scalability and energy consumption limits affecting the semiconductor industry. New computational device architectures, such as low-power solid state magnetic logic and memory-in-logic devices, have been proposed which rely on the unique properties of magnetic materials. Magnetic skyrmions, topologically protected quasi-particles, are at the core of many of the newly proposed spintronic devices. Many different materials systems have been shown hosting ferromagnetic skyrmions at room temperature. However, a magnetic field is a key ingredient to stabilize skyrmions, and this is not desirable for applications, due to the poor scalability of active components generating magnetic fields. Here we report the observation of ferromagnetic skyrmions at room temperature and zero magnetic field, stabilized through interlayer exchange coupling (IEC) between a reference magnet and a free magnet. Most importantly, by tuning the strength of the IEC, we are able to tune the skyrmion size and areal density. Our findings are relevant to the development of skyrmion-based spintronic devices suitable for general-use applications which go beyond modern nanoelectronics.

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Properties of interfaces of a phosphorene monolayer with six different low-index metal surfaces are calculated using density functional methods. Pd(111), Pd(110), Pd(100), Ti(0001), Au(110) and Ni(110) surfaces have been considered as these metals have been used as electrodes in experimental studies of phosphorene-based field effect transistor (FET) devices. In order to understand the chemistry of metal–phosphorene bonding, adsorption of individual atoms of these four metals on a phosphorene monolayer has also been studied. In addition to structural and electronic properties, barriers for charge injection at these metal–phosphorene interfaces have been studied by calculating the Schottky and tunneling barrier heights. Ti appears to be the best choice for metal electrode in phosphorene devices.