Epitaxial antiperovskite/perovskite heterostructures for materials design

We demonstrate fabrication of atomically sharp interfaces between nitride antiperovskite Mn$_{3}$GaN and oxide perovskites (La$_{0.3}$Sr$_{0.7}$)(Al$_{0.65}$Ta$_{0.35}$)O$_{3}$ (LSAT) and SrTiO$_{3}$ as paradigms of nitride-antiperovskite/oxide-perovskite heterostructures. Using a combination of scanning transmission electron microscopy (STEM), atomic-resolution spectroscopic techniques, and first-principle calculations, we investigated the atomic-scale structure, composition, and boding at the interface. We show that the epitaxial growth between the antiperovskite and perovskite compounds is mediated by a coherent interfacial monolayer that connects the two anti-structures. We anticipate our results to be a major step for the development of functional antiperovskite/perovskite heterostructures opening to harness a combination of their functional properties including topological properties for ultra low power applications

Symmetry Control of Unconventional Spin–Orbit Torques in IrO\u3csub\u3e2\u3c/sub\u3e

Spin–orbit torques generated by a spin current are key to magnetic switching in spintronic applications. The polarization of the spin current dictates the direction of switching required for energy-efficient devices. Conventionally, the polarizations of these spin currents are restricted to be along a certain direction due to the symmetry of the material allowing only for efficient in-plane magnetic switching. Unconventional spin–orbit torques arising from novel spin current polarizations, however, have the potential to switch other magnetization orientations such as perpendicular magnetic anisotropy, which is desired for higher density spintronic-based memory devices. Here, it is demonstrated that low crystalline symmetry is not required for unconventional spin–orbit torques and can be generated in a nonmagnetic high symmetry material, iridium dioxide (IrO2), using epitaxial design. It is shown that by reducing the relative crystalline symmetry with respect to the growth direction large unconventional spin currents can be generated and hence spin–orbit torques. Furthermore, the spin polarizations detected in (001), (110), and (111) oriented IrO2 thin films are compared to show which crystal symmetries restrict unconventional spin transport. Understanding and tuning unconventional spin transport generation in high symmetry materials can provide a new route towards energy-efficient magnetic switching in spintronic devices

Epitaxial La0.67Sr0.33MnO3/La0.67Ba0.33MnO3 superlattices

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Epitaxial Antiperovskite/Perovskite Heterostructures for Materials Design

Engineered heterostructures formed by complex oxide materials are a rich source of emergent phenomena and technological applications. In the quest for new functionality, a vastly unexplored avenue is interfacing oxide perovskites with materials having dissimilar crystallochemical properties. Here, we propose a unique class of heterointerfaces based on nitride antiperovskite and oxide perovskite materials as a previously unidentified direction for materials design. We demonstrate the fabrication of atomically sharp interfaces between nitride antiperovskite Mn3GaN and oxide perovskites (La0.3Sr0.7)(Al0.65Ta0.35)O3 and SrTiO3. Using atomic-resolution imaging/spectroscopic techniques and first-principles calculations, we determine the atomic-scale structure, composition, and bonding at the interface. The epitaxial antiperovskite/perovskite heterointerface is mediated by a coherent interfacial monolayer that interpolates between the two antistructures. We anticipate our results to be an important step for the development of functional antiperovskite/perovskite heterostructures, combining their unique characteristics such as topological properties for ultralow-power applications

Symmetry Control of Unconventional Spin–Orbit Torques in IrO2

Spin–orbit torques generated by a spin current are key to magnetic switching in spintronic applications. The polarization of the spin current dictates the direction of switching required for energy-efficient devices. Conventionally, the polarizations of these spin currents are restricted to be along a certain direction due to the symmetry of the material allowing only for efficient in-plane magnetic switching. Unconventional spin–orbit torques arising from novel spin current polarizations, however, have the potential to switch other magnetization orientations such as perpendicular magnetic anisotropy, which is desired for higher density spintronic-based memory devices. Here, it is demonstrated that low crystalline symmetry is not required for unconventional spin–orbit torques and can be generated in a nonmagnetic high symmetry material, iridium dioxide (IrO2), using epitaxial design. It is shown that by reducing the relative crystalline symmetry with respect to the growth direction large unconventional spin currents can be generated and hence spin–orbit torques. Furthermore, the spin polarizations detected in (001), (110), and (111) oriented IrO2 thin films are compared to show which crystal symmetries restrict unconventional spin transport. Understanding and tuning unconventional spin transport generation in high symmetry materials can provide a new route towards energy-efficient magnetic switching in spintronic devices. © 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.11Nsciescopu

Local Atomic Configuration Control of Superconductivity in the Undoped Pnictide Parent Compound BaFe2As2

Emergent superconductivity is strongly correlated with the symmetry of local atomic configuration in the parent compounds of iron-based superconductors. While chemical doping or hydrostatic pressure can change the local geometry, conventional approaches do not provide a clear pathway in predictably tuning the detailed atomic arrangement due to the parent compound’s complicated structural deformation in the presence of the tetragonal-to-orthorhombic phase transition. Here, we demonstrate a systematic approach to manipulate local structural configurations in BaFe2As2 epitaxial thin films by controlling two independent structural factors, orthorhombicity (in-plane anisotropy) and tetragonality (out-of-plane/in-plane balance), from lattice parameters. We tune superconductivity without doping utilizing both structural factors separately and controlling local tetrahedral coordination in the designed thin film heterostructures with substrate clamping and biaxial strain. We further show this allows quantitative control of the structural phase transition, the associated magnetism, and superconductivity in parent material BaFe2As2. Furthermore, this approach will advance the development of tunable thin film superconductors in a reduced dimension.This is a manuscript of an article published as Kang, Jong-Hoon, Philip J. Ryan, Jong-Woo Kim, Jonathon Schad, Jacob P. Podkaminer, Neil Campbell, Joseph Suttle et al. "Local atomic configuration control of superconductivity in the undoped pnictide parent compound BaFe2As2." ACS Applied Electronic Materials 4, no. 4 (2022): 1511-1517. DOI: 10.1021/acsaelm.2c00291. Copyright 2022 American Chemical Society. Posted with permission. DOE Contract Number(s): AC02-07CH11358, FG02-06ER46327; AC02-06CH11357; DMR-1644779; DMR-1720415

Publisher Correction: Direct imaging of the electron liquid at oxide interfaces

In the version of this Letter originally published, in two instances in Fig. 1 the layers in the cross-sectional view of the (001) interface were incorrectly labelled: in Fig. 1b SrO+ should have read SrO0; in Fig. 1c LaO+, AlO2 –, LaO+, TiO2 0, SrO+, TiO2 0 should have read LaO3 3–, Al3+, LaO3 3–, Ti4+, SrO3 4–, Ti4+. In Fig. 3c the upper-right equation read –σs = –e/2a2 but should have read –σs = e/2a2 and in Fig. 3f the lower-right equation read –σs = –e/2√3a2 but should have read σs = –e/2√3a2. These errors have now been corrected in the online version of the Letter. © 2018 The Author(s11sci