22 research outputs found
Efficient Spin-Orbit Torques in an Antiferromagnetic Insulator with Tilted Easy Plane
Electrical manipulation of spin textures inside antiferromagnets represents a
new opportunity for developing spintronics with superior speed and high device
density. Injecting spin currents into antiferromagnets and realizing efficient
spin-orbit-torque-induced switching is however still challenging due to the
complicated interactions from different sublattices. Meanwhile, because of the
diminishing magnetic susceptibility, the nature and the magnitude of
current-induced magnetic dynamics remain poorly characterized in
antiferromagnets, whereas spurious effects further complicate experimental
interpretations. In this work, by growing a thin film antiferromagnetic
insulator, {\alpha}-Fe2O3, along its non-basal plane orientation, we realize a
configuration where an injected spin current can robustly rotate the N\'eel
vector within the tilted easy plane, with an efficiency comparable to that of
classical ferromagnets. The spin-orbit torque effect stands out among other
competing mechanisms and leads to clear switching dynamics. Thanks to this new
mechanism, in contrast to the usually employed orthogonal switching geometry,
we achieve bipolar antiferromagnetic switching by applying positive and
negative currents along the same channel, a geometry that is more practical for
device applications. By enabling efficient spin-orbit torque control on the
antiferromagnetic ordering, the tilted easy plane geometry introduces a new
platform for quantitatively understanding switching and oscillation dynamics in
antiferromagnets.Comment: 21 pages, 5 figure
Dopant segregation inside and outside dislocation cores in perovskite BaSnO 3 and reconstruction of the local atomic and electronic structures
Structure and input files for the anti-phase boundary in BaSnO3 relaxation simulation.Distinct dopant behaviors inside and outside dislocation cores are identified by atomic-resolution electron microscopy in perovskite BaSnO3 with considerable consequences on local atomic and electronic structures. Driven by elastic strain, when A-site designated La dopants segregate near a dislocation core, the dopant atoms accumulate at the Ba sites in compressively strained regions. This triggers formation of Ba-vacancies adjacent to the core atomic sites resulting in reconstruction of the core. Notwithstanding the presence of extremely large tensile strain fields, when La atoms segregate inside the dislocation core, they become B-site dopants, replacing Sn atoms and compensating the positive charge of the core oxygen vacancies. Electron energy-loss spectroscopy shows that the local electronic structure of these dislocations changes dramatically due to segregation of the dopants inside and around the core ranging from formation of strong La-O hybridized electronic states near the conduction band minimum to insulator-to-metal transition
Mending cracks atom-by-atom in rutile TiO2 with electron beam radiolysis
Abstract Rich electron-matter interactions fundamentally enable electron probe studies of materials such as scanning transmission electron microscopy (STEM). Inelastic interactions often result in structural modifications of the material, ultimately limiting the quality of electron probe measurements. However, atomistic mechanisms of inelastic-scattering-driven transformations are difficult to characterize. Here, we report direct visualization of radiolysis-driven restructuring of rutile TiO2 under electron beam irradiation. Using annular dark field imaging and electron energy-loss spectroscopy signals, STEM probes revealed the progressive filling of atomically sharp nanometer-wide cracks with striking atomic resolution detail. STEM probes of varying beam energy and precisely controlled electron dose were found to constructively restructure rutile TiO2 according to a quantified radiolytic mechanism. Based on direct experimental observation, a “two-step rolling” model of mobile octahedral building blocks enabling radiolysis-driven atomic migration is introduced. Such controlled electron beam-induced radiolytic restructuring can be used to engineer novel nanostructures atom-by-atom