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Antiferromagnetic insulators are a ubiquitous class of magnetic materials, holding the promise of low-dissipation spin-based computing devices that can display ultra-fast switching and are robust against stray fields. However, their imperviousness to magnetic fields also makes them difficult to control in a reversible and scalable manner. Here we demonstrate a novel proof-of-principle ionic approach to control the spin reorientation (Morin) transition reversibly in the common antiferromagnetic insulator α-Fe2O3 (haematite) - now an emerging spintronic material that hosts topological antiferromagnetic spin-textures and long magnon-diffusion lengths. We use a low-temperature catalytic-spillover process involving the post-growth incorporation or removal of hydrogen from α-Fe2O3 thin films. Hydrogenation drives pronounced changes in its magnetic anisotropy, Néel vector orientation and canted magnetism via electron injection and local distortions. We explain these effects with a detailed magnetic anisotropy model and first-principles calculations. Tailoring our work for future applications, we demonstrate reversible control of the room-temperature spin-state by doping/expelling hydrogen in Rh-substituted α-Fe2O3.

Benefiting from a high quantum efficiency, low thermal emittance, and large absorption coefficient, InxGa1−xAs is an excellent group III–V compound for negative electron affinity (NEA) photocathodes. As the emission layer, InxGa1−xAs, where x = 0.15, has the optimal performance for detection in the near-infrared (NIR) region. Herein, an NEA In0.15Ga0.85As photocathode with Al0.63Ga0.37As as the buffer layer is designed in the form of a transmission mode module. The electronic band structures and optical properties of In0.15Ga0.85As and Al0.63Ga0.37As are calculated based on density functional theory. The time response characteristics of the In0.15Ga0.85As photocathode have been fully investigated by changing the photoelectron diffusion coefficient, the interface recombination velocity, and the thickness of the emission layer. Our results demonstrate that the response time of the In0.15Ga0.85As photocathode can be reduced to 6.1 ps with an incident wavelength of 1064 nm. The quantum efficiency of the In0.15Ga0.85As photocathode is simulated by taking into account multilayer optical thin film theory. The results indicate that a high quantum efficiency can be obtained by parameter optimization of the emission layer. This paper provides significant theoretical support for the applications of semiconductor photocathodes in the near-infrared region, especially for the study of ultrafast responses in the photoemission process. [ABSTRACT FROM AUTHOR]

High quality rutile Ti 1- x Sn x O 2 nanofilms were successfully grown in a layer-by-layer mode at a moderately low temperature of 400 °C using pulsed laser deposition (PLD). High solid solubility of up to x = 0.216 has been achieved in the Ti 1- x Sn x O 2 films despite theoretical prediction by Density functional theory (DFT) of large formation energy (∼5.64 eV) required for the substitutional alloy to exist at such high Sn concentration. The resultant films have smooth interfaces and step-terraced surfaces with well controlled stoichiometry and are optically transparent. Sn L 3 -edge Extended X-ray absorption fine structure (EXAFS) reveals the substitution of Sn 4+ in the Ti 4+ lattice sites of TiO 2 . The lattice spacing along [110] increases linearly with increment in x due to substitution of Sn 4+ ions in the Ti lattice sites of the Ti 1- x Sn x O 2 films. X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering (RBS) show that Sn is uniformly distributed on the surface and in the bulk of the films. These results are crucial when considering Ti 1- x Sn x O 2 with suitable composition for making TiO 2 based quantum structures in advanced optoelectronic devices and solar energy materials, where high-quality crystalline thin film-substrates are important. [ABSTRACT FROM AUTHOR]