Quasibrittle plastic yielding is a salient feature of well-annealed glassy materials. We show that a similar mechanical response is characteristic of perfect crystals after they experience mechanically-induced massive nucleation of dislocations. We argue that such ‘preparation’ effectively converts a mechanically crystalline sample into a mechanically pseudoamorphous one. To understand the nature of the associated transformation we study a model 2D crystal subjected to AQS driving. We show that pristine crystals ‘primed’ in this way exhibit both pre- and postyield dislocation avalanches with power-law statistics. The value of the computed exponents is indicative of self-induced marginal stability. Our main tool is the novel mesoscopic tensorial model (MTM) of crystal plasticity representing a conceptual trade-off between continuum and atomic descriptions. It captures the specificity of crystals with different lattice symmetry at relatively low computational cost while relying minimally on phenomenology. Rather strikingly, MTM allows one to deal with a statistically meaningful number of dislocations while accounting in a geometrically exact way for finite deformations. The obtained results challenge the prevailing opinion that crystal and amorphous plasticity are fundamentally different phenomena. As MTM does not deal with dislocations directly, our work reinforces the idea that in both cases it is the elastic incompatibility which evolves through intermittent avalanches.

Two-dimensional topological insulators (2D TIs) have emerged as a cornerstone of next-generation spintronic technologies because of their robust, dissipationless edge states protected by time-reversal symmetry. Initial realizations of 2D TIs have primarily focused on materials with strong intrinsic spin–orbit coupling capable of driving band inversion, an approach that significantly constrains the accessible materials landscape. More recently, a paradigm shift has occurred toward engineering topological phases in van der Waals (vdW) heterostructures, where nontrivial band topology can arise from interfacial coupling rather than relying solely on intrinsic material properties. This framework provides an exceptionally versatile platform with multiple tunable degrees of freedom, including stacking configuration, twist angle, and chemical functionalization, allowing systematic manipulation of the band topology. Furthermore, external stimuli, such as electric fields, strain, and light–matter coupling, enable dynamic and reversible control of the topological character. The combined use of vdW interface engineering and external modulation allows the realization of 2D TI phases even in otherwise topologically trivial systems, substantially expanding the accessible materials landscape. This Research Update reviews key milestones in the development of vdW-engineered 2D topological quantum materials, critically assesses outstanding theoretical and experimental challenges, and outlines promising directions for future breakthroughs.

Electric bubbles are sub-10-nm spherical ferroelectric domains promising intriguing functional properties suitable for the next-generation solid-state electronic devices. However, the understanding of their dynamic conductivities, a paramount factor in their circuit integration, remains limited. Here we investigate conduction properties of ferroelectric bubbles using a combination of scanning probe microscopy and first-principles-based simulations. Our experiments reveal that the bubbles exhibit rectifying current-voltage characteristics with ultrahigh direct current densities, attributed to tunneling. Under external electric field, conductivity is maintained or enhanced as long as the original bubble configuration remains stable. On the other hand, when the dipolar configuration is fully disrupted by mechanical force, the conductivity of mechanically switched downward domains decreases by 50%. Our simulations reveal the role of inhomogeneous depolarizing fields and screening conditions which allows for dynamical tuning of the tunneling transport. This ability to control conductivity in ferroelectric bubbles through external stimuli opens new possibilities for their application in future electronic and functional devices.

This work presents a comprehensive investigation of the structural, magnetic, and electronic properties of the double perovskite ${\mathrm{Ba}}_2\mathrm{CoMo}{\mathrm{O}}_6$ (BCMO). Single crystals were grown via floating-zone and Czochralski growth techniques and characterized using a set of complementary methods. X-ray diffraction analysis confirmed that BCMO crystallizes in a face-centered-cubic (fcc) structure with space group Fm-3m. Magnetic susceptibility measurements exhibit antiferromagnetic ordering below $T_{\mathrm{N}}=20.1\left(1\right)$ K. A spin-flop transition is observed at 26.5 kOe. Heat capacity measurements and entropy analysis are consistent with a $J_{\mathrm{eff}}=1/2$ ground state for $\mathrm{C}{\mathrm{o}}^{2+}$ ions. X-ray absorption spectroscopy provided insight into the local electronic structure, revealing the spin-orbit and crystal-field effects. The cluster-model analysis yields a $g$ factor of 4.36, consistent with a spin-orbit-entangled ground state. Surface photovoltage spectroscopy demonstrates a strong near-surface optical response with an onset near 1.5 eV and a pronounced feature at 2.65 eV, consistent with visible-range Co-O-Mo transitions in line with related Ba-based double perovskites, highlighting its potential for spintronic and energy-conversion applications.

Eshelby's energy-momentum tensor and Rice's $J$-integral provide path-independent measures of configurational forces driving defects and cracks in elastic media. Their applicability, however, breaks down in materials where distributed anelastic rearrangements screen elastic stresses over a screening length ${\left|\kappa \right|}^{-1}$. Here, we generalize these constructs to mechanically screened media dominated by dipolar screening. We identify two distinct regimes associated with real and imaginary $\kappa$, leading to qualitatively different responses. Real screening induces exponential attenuation of elastic fields, and in the context of cracks, suppresses energy flow into crack tips, resulting in effective toughening. In contrast, imaginary screening produces spatially oscillatory fields that enhance energy transport, promoting fragility. Our results extend the foundational tools of fracture mechanics to screened elastic media and reveal regimes distinct from classical linear elastic fracture mechanics.

Magnetic interatomic potentials need to account for coupled lattice and spin degrees of freedom, yet constructing reliable training sets remains costly because noncollinear first-principles labels are expensive. Active learning can mitigate this cost, provided that the uncertainty estimate is physically meaningful for the magnetic-response targets that drive spin reorientation. Here we introduce equivariant evidential deep learning for spin-lattice potentials $\left({\mathrm{e}}^2\mathrm{SLP}\right)$, a magnetic uncertainty-learning method that formulates the projected spin-force likelihood and the corresponding epistemic uncertainty in the tangent plane orthogonal to the local spin direction. This geometry is consistent with the constrained-moment labels, which contain no independent radial response, and yields a structure-level projected-spin-force uncertainty score for candidate selection. Using bulk ${\mathrm{BiFeO}}_3$ and monolayer ${\mathrm{CrTe}}_2$ as benchmark systems, we show that this score correlates strongly with prediction errors and that the full ${\mathrm{e}}^2\mathrm{SLP}$ selection, training, and fine-tuning workflow lowers energy, force, and projected spin-force errors relative to random sampling. For monolayer ${\mathrm{CrTe}}_2$, round-by-round comparisons show accuracy competitive with a four-model committee, while a four-seed ablation separates the contributions of uncertainty-guided selection and ${\mathrm{e}}^2\mathrm{SLP}$ training followed by fine tuning. ${\mathrm{e}}^2\mathrm{SLP}$ thus provides a single-model tangent-plane uncertainty criterion for data-efficient construction of magnetic machine-learning interatomic potentials.

The interplay of magnetism, structural phase transition, and nontrivial spin texture in magnetic shape memory alloys (MSMAs) offers exciting avenues for exploring exotic physical phenomena and potential applications in spintronic devices. Here, we report the anomalous Hall transport behavior in a robust premartensite (PM)-phase-transforming ${\mathrm{Ni}}_{49}{\mathrm{Mn}}_{34}{\mathrm{In}}_{16.2}{\mathrm{Al}}_{0.8}$ MSMA. Temperature-dependent magnetization data reveal a phase transition from austenite to a robust PM phase at approximately 270 K, further confirmed by temperature-dependent synchrotron x-ray powder diffraction (SXRPD) measurements. The PM phase remains stable over a wide temperature range (270 K down to 100 K), as observed from SXRPD. Anomalous Hall transport measurements performed in both the austenite and PM phases indicate that the anomalous Hall effect originates predominantly from the intrinsic momentum-space Berry curvature. A large topological Hall effect (THE), associated with the real-space Berry curvature, is observed near the PM transition $(\sim 270\mathrm{K})$ and decreases with decreasing temperature. The maximum THE observed at the PM phase boundary suggests the presence of nontrivial spin textures. These findings provide new insights into the coupling between electronic transport, magnetic configurations, and structural transformations in MSMAs, paving the way for the design of materials for spintronic applications.

Carpy-Galy ${\mathrm{LaTaO}}_4$ undergoes a structural sequence linking the antipolar monoclinic $P{2}_1/c$ ground state and the polar orthorhombic $Cmc{2}_1$ phase through an incommensurately modulated regime. First-principles calculations identify a metastable polar monoclinic $P{2}_1$ phase as a commensurate intermediate in the phase-transition landscape. As a common subgroup of $P{2}_1/c$ and $Cmc{2}_1$, $P{2}_1$ provides a symmetry-connected route between the established polymorphs. Mode-resolved energy surfaces for these symmetry-breaking pathways show that coupling between the respective primary order parameters and an isosymmetric relaxation stabilizes the $P{2}_1$ minimum along both pathways. Consequently, the $P{2}_1/c\to P{2}_1$ transformation has a finite energy barrier, while a restricted soft-mode model retains competing $P{2}_1$ and $Cmc{2}_1$ basins over an illustrative range of harmonic stiffness. Lattice-metric and neutron-diffraction comparisons indicate a shared displacement character between the calculated commensurate state and the experimental incommensurately modulated orthorhombic (IC-o) modulation, supporting the use of $P{2}_1$ as a commensurate structural reference for IC-o. Finally, composition-dependent energetics suggest chemical routes for tuning polar-antipolar competition.

A range of alloying candidates have been identified for beta gallium oxide ($\beta \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$) as a means of tuning its electronic properties, primarily the band gap. Scandium has been recognized as a promising alloying candidate, but its effect on $\beta \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$'s electronic, structural, and defect behavior must be better understood to enable further development. Here, Czochralski-grown (100) $\beta \text{−}{\left({\mathrm{Sc}}_{0.06}{\mathrm{Ga}}_{0.94}\right)}_2{\mathrm{O}}_3$ crystals were investigated using atomic-resolution scanning transmission electron microscopy, monochromated electron energy loss spectroscopy, and first-principles simulations. These results show that Sc preferentially occupies octahedral Ga sites and increases the material's band gap from 4.8 eV to 4.92 eV when alloyed with 10 mol% Sc. It is also demonstrated that the alloying of Sc can result in unique extended defect formation in both intrinsic and mechanically deformed $\beta \text{−}{\left({\mathrm{Sc}}_{0.06}{\mathrm{Ga}}_{0.94}\right)}_2{\mathrm{O}}_3$. The structure of a unique planar defect in the as-grown crystal was determined to be a set of closely spaced, (100)-oriented stacking faults resulting in a unique atomic projection. Mechanical deformation of the crystal, performed to help understand intrinsic defect structure, resulted in the identification of an atomic configuration within a stacking fault heavily influenced by local strain, which we term a “strained stacking fault”. No widespread formation of point defects or dislocations was observed in the as-grown crystal. These results reveal the ability of unique extended defects, such as multiple stacking faults in close proximity, to form in $\beta \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$ systems when alloyed. These findings provide insight into the potential of $\beta \text{−}{\left({\mathrm{Sc}}_{\mathrm{x}}{\mathrm{Ga}}_{1-x}\right)}_2{\mathrm{O}}_3$ alloys to produce substrates with a range of electronic and structural properties, enabling further development of $\beta \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$ for next-generation power semiconductor applications.

Dislocation-mediated plasticity in perovskite oxides exhibits strong chemistry dependence, yet the microscopic origins of contrasting plastically deformable and brittle behaviors across chemically similar compounds remain poorly understood. In this work, a phase field dislocation dynamics (PFDD) framework informed by ab initio generalized stacking fault energy ($\gamma$-surface) calculations is applied to investigate dislocation core structure and glide resistance in four cubic perovskite oxides: ${\text{SrTiO}}_3$, ${\text{CaTiO}}_3$, ${\text{KNbO}}_3$, and ${\text{KTaO}}_3$. Equilibrium dissociation of full $\langle 110\rangle$ dislocations into collinear $\frac{1}{2}\langle 110\rangle$ partial dislocations separated by an antiphase boundary is observed across all chemistries, with partial separation distances in good agreement with available experimental and atomistic benchmarks. The potassium-containing perovskites develop significantly wider dissociated cores than ${\text{SrTiO}}_3$ and ${\text{CaTiO}}_3$, consistent with their lower antiphase boundary energies. Athermal Peierls stress calculations reveal that ${\text{CaTiO}}_3$ exhibits the highest lattice resistance, while ${\text{SrTiO}}_3$ exhibits the lowest, reproducing the experimentally observed ranking of plastic deformability across this perovskite series. Additionally, a two-stage glide mechanism is identified in ${\text{KNbO}}_3$ and ${\text{KTaO}}_3$, wherein the leading and trailing partial dislocations depin under distinct stress thresholds. These results demonstrate that PFDD provides an efficient and transferable mesoscale framework for systematically linking ab initio fault energetics to dislocation dynamics across complex oxide chemistries.

This study unveils the anomalous Nernst coefficient enhancement mechanism in ferromagnetic Co/semiconductor Si multilayer films featured by drastically low thermal conductivity unlike conventional ferromagnetic metal/ nonmagnetic metal multilayer films. In a context where a lot of previous studies of multilayer films have discussed the mysterious interface effect, we identified the origin of anomalous Nernst coefficient enhancement effect at the interface by isolating thermoelectric properties of interface layers. It was found that this enhancement effect was attributed to the strengthened interface carrier scatterings. Thanks to this interface effect, Co/Si multilayer films exhibited an order of magnitude higher anomalous Nernst coefficient than Co films, resulting in $\sim 30$ times higher thermoelectric power factor. This direct evidence of the interface effect will open an avenue for high-performance thermoelectric materials based on anomalous Nernst effect.

We report a detailed study on the structural, angle-dependent magnetic and magnetotransport properties of highly anisotropic off-stoichiometric ${\mathrm{CeCuBi}}_2$ single crystals. Our results reveal ${\mathrm{CeCuBi}}_2$ as an anisotropic Kondo antiferromagnet exhibiting complex field-induced magnetic behavior and unusual magnetotransport properties. Magnetic susceptibility and specific heat measurements reveal antiferromagnetic (AFM) ordering below $T_N\sim 14\mathrm{K}$ with strong anisotropy and weak heavy-fermion behavior. Electrical transport measurements show highly anisotropic resistivity and a broad hump around $\sim 47\mathrm{K}$, indicative of Kondo-driven heavy-fermion behavior. Magnetization measurements reveal multiple field-induced metamagnetic phases, while ac susceptibility measurements indicate slow spin dynamics and spin-glass-like behavior in intermediate field-induced magnetic states. Furthermore, we observe large and strongly anisotropic magnetotransport responses, including room-temperature magnetoresistance of $\sim 22\%$ at 300 K and 9 T and butterflylike anisotropic magnetoresistance with AMR values reaching $\sim 10.9\%$. These results highlight a strong interplay among Kondo correlations, magnetic anisotropy, and field-tunable spin configurations, making ${\mathrm{CeCuBi}}_2$ a possible platform for exploring correlated and anisotropic quantum phenomena.

The established guiding principle for pulsed laser deposition (PLD) of high-quality ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta }$ (YBCO) superconducting films suggests that the optimal target-to-substrate distance (TSD) lies near the visible tip of the laser-induced plume, with deviations from this point expected to degrade film properties. We modified our PLD system to allow precise external TSD adjustment over a 110-mm range and systematically studied its influence on the microstructure and electromagnetic properties of YBCO thin films. Our analysis, referencing plume-propagation models and growth processes, reveals that the optimal TSD range can, in fact, be extended under a relatively high laser fluence, depending on the desired film performance and properties. We identify four TSD regimes, each exhibiting unique film characteristics. Notably, we demonstrate that high-quality superconducting properties and crystallinity are preserved across a broad 50-mm TSD window, yielding films with variable thickness and surface structures. This tunability enhances the potential for applications in electronics and high power handling, where tailored combinations of surface structure and/or electromagnetic properties are required. Furthermore, we propose that TSD-dependent variations in flux and growth rate provide a straightforward and effective approach to probe plume (plasma) composition during laser ablation, offering insights into deposition dynamics.

Lead-cooled fast reactors impose harsh environments on the structural materials, including high damage doses, high temperatures and corrosive liquid lead. To withstand these environments, advanced steel concepts, such as a composite of 15-15Ti and FeCrAl, have been proposed as fuel cladding. Microstructural evolution of alloys is governed by fundamental properties, including the vacancy formation and migration energies, yet such data for novel alloy compositions is sparse. In this work, an extensive set of vacancy formation and migration energies in two alloys, 15-15Ti and FeCrAl, was calculated from first principles, employing density functional theory. Special quasirandom structures were generated for both alloys, and different magnetic states of the alloys were simulated. It was found that the vacancy formation energy is highly influenced by the chemical and magnetic environment in 15-15Ti, while in FeCrAl the size mismatch between Fe and the alloying elements dominates. The vacancy formation energy was calculated by two different density functional theory formulations, showing excellent agreement. The vacancy migration energy was found to be governed by changes in the magnetic and chemical environment as the atom migrates. Based on these findings, temperature-averaged behaviors of vacancies in the alloys are derived, which can be further used to define effective vacancy formation and migration energies at reactor-relevant temperatures. The effective vacancy formation and migration energies can be used to predict temperature-variable shifts needed to accommodate the higher dose rate when using ion irradiation to emulate neutron irradiation.

Thermal-desorption spectroscopy (TDS) is widely used to characterize hydrogen-isotope retention in plasma-facing tungsten, but a measured spectrum does not uniquely identify the underlying microscopic defect configurations: different kinetic parameters can produce similar curves, while distinct vacancy-hydrogen configurations may have nearly the same binding energy. To account for these ambiguities, we formulate a Bayesian inversion that determines the range of detrapping-energy spectra consistent with a measured curve and reports all defect configurations allowed by those energies. Applied to a published deuterium-TDS curve of damaged tungsten, the method successfully resolves two detrapping-energy peaks centered at 1.58 [1.49, 1.70] and 1.97 [1.87, 2.08] eV, where each bracket contains 90% of the inferred probability. Across the four predamage conditions, the changing spectra can be described by the same two energy components while the lower-energy component loses relative weight as predamage temperature rises; both features also recur in an independent experiment. Tests on curves with known inputs show that peak temperatures are better determined than the detrapping energies behind them, and that the inferred energies still correspond to many vacancy-hydrogen configurations. The spectral evolution thus points to changing relative contributions from recurring trapping-energy families, without identifying a unique microscopic defect population.

The filling of the large van der Waals gap in Transition Metal Dichalcogenides (TMDs) often leads to lattice and electronic instabilities, which prelude the onset of a rich phenomenology. Motivated by previous results from macroscopic measurements, we investigate the electronic structure of the TMDs ${\mathrm{ZrTe}}_2$ and Ni intercalated ${\mathrm{ZrTe}}_2$ $({\mathrm{Ni}}_x{\mathrm{ZrTe}}_2,$ $x\approx 0.05)$ employing angle-resolved photoemission spectroscopy (ARPES). We readily identify in ${\mathrm{Ni}}_x{\mathrm{ZrTe}}_2$ two flat bands, most likely associated with localized Ni-derived $3d$-states, at about $\approx -0.7\mathrm{eV}$ and $\approx -1.2\mathrm{eV}$ in binding energy. More significantly, at low $T$, we identify an electronic structure reconstruction in ${\mathrm{Ni}}_x{\mathrm{ZrTe}}_2$, which halves the electronic periodicity along the $k_z$ direction. This is reminiscent of a commensurate band folding with wave vector $q=(0,0,\pi )$. A mean-field model for a charge density wave (CDW) transition driven by interband hole-hole interactions is solved with inputs from the experimentally determined electronic band structure. Comparison between theory and experiments unveils a CDW transition in ${\mathrm{Ni}}_x{\mathrm{ZrTe}}_2$, for which the gap opens above the Fermi level. Our findings invite further investigation into the structural properties of intercalated ${\mathrm{ZrTe}}_2$.

We report the anomalous characteristics of magnetostructural phases in the vicinity of the orbital/charge-ordered state ($T_{\mathrm{OO}/\mathrm{CO}}\sim 220\mathrm{K}$) below the antiferromagnetic (AFM) Néel temperature ($T_{\mathrm{N}}\sim 130\mathrm{K}$) of the correlated electron system ${\mathrm{Ca}}_{0.75}{\mathrm{Sm}}_{0.25}{\mathrm{MnO}}_3$ by means of neutron diffraction, field-dependent heat-capacity, and magnetometry studies. Our neutron diffraction study reveals an apparent coexistence of two commensurate magnetic phases with the propagation vectors ${\mathit{k}}_{\mathit{C}}=(1/2,1/2,0)$ and ${\mathit{k}}_{\mathit{E}}=(1/2,\epsilon ,0)$ forming probably a $CE$ phase, with $\epsilon \sim 0.267\left(3\right)$ close to 1/4, indicating that the magnetic unit cell coincides with the enlarged superstructure of dimensions $a\times 4b\times c$. It was found that the moments of both magnetic phases are AFM-coupled along all directions forming an $A$- or a $G$-type ordering, where the magnetic moments of the $C$- and $E$-type phases are aligned within the $ab$ plane and along the $c$ axis, respectively. In the noncollinear magnetic structure, the $C$-type phase can be described with the irreducible representations of ${\mathrm{\Gamma }}_6(A_x,G_y)$ and ${\mathrm{\Gamma }}_8(G_x,A_y)$, where the Mn moments are oriented parallel to the directions [110] and $\left[1\overline{1}0\right]$. Moreover, phenomena such as field-induced metamagnetic transitions ($H_{\mathrm{T}}\sim 120\mathrm{kOe}$ at 3 K), critical behavior of specific heat ($C_P=A{|T-T_{\mathrm{N}}|}^{-\alpha }$), negative exchange bias effect ($H_{\mathrm{EB}}$), and a zero-crossover of magnetic entropy change ($\mathrm{\Delta }{S}_{\mathrm{M}}$) are newly observed in this unique composition.

The transition metal trichalcogenides (TMTs) are an interesting class of layered 2D materials that have strong anisotropic electrical and optical properties. We report on the polarization-dependent nonlinear optical response of exfoliated crystals at the third harmonic using nonresonant excitation with a 1560 nm femtosecond laser. All members of the TMT crystal family explored $({\mathrm{ZrS}}_3,$ ${\mathrm{HfS}}_3,$ ${\mathrm{TiS}}_3, \text{and} {\mathrm{NbS}}_3)$ display large anisotropy in their polarized third harmonic generation signal, with anisotropy ratios as large as ${\chi }_{11}/{\chi }_{22}\approx 6.5$. From the expected nonlinear dependence of these monoclinic and triclinic crystals, we extract the relative nonlinear susceptibility coefficients. We find that the anisotropy ratio is largest for ${\mathrm{ZrS}}_3$ and decreases across the family, a trend we associate with the proximity of the third harmonic energy to the strongly $b$-polarized absorption edge of each material. ${\mathrm{NbS}}_3$, the only triclinic crystal, displays a pronounced anisotropy in thick flakes that is strongly reduced in the thinnest flakes, which we attribute to a partial relaxation of the Peierls-type Nb–Nb dimerization that underlies the triclinic distortion. The large anisotropic nonlinear response in this crystal family sets it apart from other 2D materials and makes them particularly attractive for further investigation.

This study investigates the impact of a Pt underlayer on the antiferromagnetic properties of epitaxial NiO(001) films, focusing on the antiferromagnetic domain structure and interfacial exchange coupling. Two types of epitaxial NiO films were prepared: one directly deposited on an MgO(001) substrate and the other with a 10-nm-thick Pt layer inserted between the NiO film and the MgO substrate. Despite both films exhibiting epitaxial growth, detailed structural analyses reveal that the insertion of Pt underlayer leads to the strain relaxation and introduces the misfit dislocations at the Pt/NiO interface. Moreover, the exchange bias and coercive fields of the adjacent CoFeB layer are significantly enhanced in the sample with the Pt underlayer. X-ray magnetic linear dichroism photoemission electron microscopy (XMLD-PEEM) visualizes a drastic reduction in the antiferromagnetic domain size by the Pt insertion. The disappearance of micrometer-scale XMLD contrast and the emergence of an in-plane Néel vector orientation indicate that the strain relaxation and interfacial disorder introduced by the Pt underlayer strongly modify the antiferromagnetic domain configuration. These results demonstrate that the Pt underlayer serves as an effective structural and magnetic control parameter in epitaxial NiO, providing a pathway to tailor antiferromagnetic domain structures and interfacial exchange coupling for NiO-based spintronic devices.