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Here, we present a comprehensive study on atomic-scale in-situ biasing/heating scanning transmission electron microscopy ((S)TEM) of Al-amorphous SiO2–SiC interface. The investigation includes electrical, chemical, and structural analysis of the interface at different temperatures (25–600 °C). The results show that at ~ 500 °C the electrical (three-orders of magnitude resistivity drop), chemical (dissolution of SiO2 amorphous layer), and microstructural features (e.g. formation of Al2O3, Si and Al4C3) of the interface start to change. According to the results, amorphous SiO2 dissolves in Al, leading to formation of α-Al2O3 and Si within the Al. In contrast, elemental interdiffusion (Al3+ ⇄ Si4+) between Al and SiC occurs resulting in formation of Al4C3. From the results, we can infer that reaction mechanism between Al and crystalline SiC is different with that between Al and SiO2 amorphous phase. It is believed that structural similarities between SiC and Al4C3 play an important role in paving the way for elemental interdiffusion.

Permanent magnets draw their properties from a complex interplay, across multiple length scales, of the composition and distribution of their constituting phases, that act as building blocks, each with their associated intrinsic properties 1. Gaining a fundamental understanding of these interactions is hence key to decipher the origins of their magnetic performance2 and facilitate the engineering of better-performing magnets, through unlocking the design of the “perfect defects” for ultimate pinning of magnetic domains3. Here, we deployed advanced multiscale microscopy and microanalysis on a bulk Sm2(CoFeCuZr)17 pinning-type high-performance magnet with outstanding thermal and chemical stability 4. Making use of regions with different chemical compositions, we showcase how both a change in the composition and distribution of copper, along with the atomic arrangements enforce the pinning of magnetic domains, as imaged by nanoscale magnetic induction mapping. Micromagnetic simulations bridge the scales to provide an understanding of how these peculiarities of micro- and nanostructure change the hard magnetic behaviour of Sm2(CoFeCuZr)17 magnets. Unveiling the origins of the reduced coercivity allows us to propose an atomic-scale defect and chemistry manipulation strategy to define ways toward future hard magnets.

Powder bed fusion of metals using a laser beam (PBF-LB/M) is an established additive manufacturing (AM) method that can be used to fabricate geometrically complex NdFe-B magnets. However, the magnetic properties of Nd-Fe-B magnets manufactured by PBF-LB/M are typically inferior to conventionally produced magnets. To overcome this drawback, we modified the surface of the permanent magnet feedstock powder with 1 wt.% surfactant-free Ag nanoparticles (NPs) supporting the formation of relevant phases required for permanent magnetic performance to achieve a suitable micro- and nanostructure after AM. Our study is accompanied by finite element simulations, revealing the impact and dependency of process parameters during PBF-LB/M: a wide temperature field with a high-gradient profile in the front and on the bottom of an overheated region, implying a vast local heating/cooling rate and in-process high thermal stress. We found experimentally that the as-built part density can be affected by both the laser power and scan speed, causing a reduction in density as both parameters increase. The functionality and microstructural properties are also investigated via VSM, HR-SEM, EDX, EBSD, and exemplarily with HR-TEM-EDX and APT. Our study found that modifying MQP-S with Ag NPs increases the coercivity by approximately 20%, which we correlate to a decreased grain size. Additionally, we identified three distinct phases in the modified and unmodified samples, where Ag is primarily found in the intergranular and Nd-rich phases of the as-built parts. Overall, the study's findings contribute to the understanding of the factors that affect the quality and magnetic properties of Nd-Fe-B magnets fabricated through PBF-LB/M and provide valuable insights for further research in this area.

SiBN ceramics are widely considered to be the most promising material for microwave-transparent applications in harsh environments owing to its excellent thermal stability and low dielectric constant. This work focuses on the synthesis and ceramization of single-source precursors for the preparation of SiBN ceramics as well as the investigation of the corresponding microstructural evolution at high temperatures including molecular dynamic simulations. Carbon- and chlorine-free perhydropolysilazanes were reacted with borane dimethyl sulfide complex at different molar ratios to synthesize single-source precursors, which were subsequently pyrolyzed and annealed under N2 atmosphere (without ammonolysis) to prepare SiBN ceramics at 1100, 1200, and 1300 °C with high ceramic yield in contrast to previously widely-used ammonolysis synthesis process. The obtained amorphous SiBN ceramics were shown to have remarkably improved thermal stability and oxidation resistance compared to amorphous silicon nitride. Particularly, the experimental results have been combined with molecular dynamics simulation to further study the amorphous structure of SiBN and the atomic-scale diffusion behavior of Si, B, and N at 1300 °C. Incorporation of boron into the Si—N network is found to suppress the crystallization of the formed amorphous silicon nitride and hence improves its thermal stability in N2 atmosphere.

Hafnium oxide plays an important role as a dielectric material in various thin-film electronic devices such as transistors and resistive or ferroelectric memory. The crystallographic and electronic structure of the hafnia layer often depends critically on its composition and defect structure. Here, we report two novel defect-stabilized polymorphs of substoichiometric HfO

Carbon supported metallic nanomaterials are of great interest due to their low-cost, high durability and promising functional performance. Herein, a highly active oxygen evolution reaction (OER) electrocatalyst comprised of defective carbon shell encapsulated metal (Fe, Co, Ni) nanoparticles and their alloys supported on in-situ formed N-doped graphene/carbon nanotube hybrid is synthesized from novel single-source-precursors (SSP). The precursors are synthesized by a facile one-pot reaction of tannic acid with polyethylenimine and different metal ions and subsequent pyrolysis of the SSP. Benefiting from the heteroatom doping of carbon and formation of well-encapsulated metal/alloy nanoparticles, the obtained FeNi@NC-900 catalyst possesses lowest overpotentials of 310 mV to achieve a current density of 10 mA cm

Utilizing the molecular beam epitaxy technique, a nanoscale thin-film magnet of c-axis-oriented Sm2Co17 and SmCo5 phases is stabilized. While typically in the prototype Sm(Co, Fe, Cu, Zr)7.5-8 pinning-type magnets, an ordered nanocomposite is formed by complex thermal treatments, here, a one-step approach to induce controlled phase separation in a binary Sm-Co system is shown. A detailed analysis of the extended X-ray absorption fine structure confirmed the coexistence of Sm2Co17 and SmCo5 phases with 65% Sm2Co17 and 35% SmCo5. The SmCo5 phase is stabilized directly on an Al2O3 substrate up to a thickness of 4 nm followed by a matrix of Sm2Co17 intermixed with SmCo5. This structural transition takes place through coherent atomic layers, as revealed by scanning transmission electron microscopy. Highly crystalline growth of well-aligned Sm2Co17 and SmCo5 phases with coherent interfaces result in strong exchange interaction, leading to enhanced magnetization and magnetic coupling. The arrangement of Sm2Co17 and SmCo5 phases at the nanoscale is reflected in the observed magnetocrystalline anisotropy and coercivity. As next-generation permanent magnets require designing of materials at an atomic level, this work enhances our understanding of self-assembling and functioning of nanophased magnets and contributes to establishing new concepts to engineer the microstructure for beyond state-of-the-art magnets.

Reversible antiferroelectric-ferroelectric phase transitions were recently observed in a series of SrSnO3-modified NaNbO3 lead-free antiferroelectric materials, exhibiting well-defined double polarization hysteresis loops at ambient conditions. Here, transmission electron microscopy was employed to investigate the crystallographyand domain configuration of this newly designed system via electron diffraction and centered dark-field imaging. It was confirmed that antiferroelectricity is maintained in all compositions, manifested by the characteristic ¼ superlattice reflections in the electron-diffraction patterns. By investigating the antiferroelectric domains and domain boundaries in NaNbO3, we demonstrate that antiphase boundaries are present and their irregular periodicity is responsible for the streaking features along the ¼ superlattice reflections in the electron-diffraction patterns. The signature domain blocks observed in pure NaNbO3 are maintained in the SrSnO3-modified ceramics, but disappear when the amount of SrSnO3 reaches 7 mol.%. In particular, a well-defined and distinct domain configuration is observed in the NaNbO3 sample modified with 5 mol.% SrSnO3, which presents a parallelogram domain morphology.

Ni-Mn-based Heusler alloys, in particular all-d-metal Ni(-Co)-Mn-Ti, are highly promising materials for energy-efficient solid-state refrigeration as large multicaloric effects can be achieved across their magnetostructural martensitic transformation. However, no comprehensive study on the crucially important transition entropy change Δs exists so far for Ni(-Co)-Mn-Ti. Here, we present a systematic study analyzing the composition and temperature dependence of Δst. Our results reveal a substantial structural entropy change contribution of approximately 65 J(kgK)-1, which is compensated at lower temperatures by an increasingly negative entropy change associated with the magnetic subsystem. This leads to compensation temperatures Tcomp of 75 K and 300 K in Ni35Co15Mn50-yTiy and Ni33Co17Mn50-yTiy, respectively, below which the martensitic transformations are arrested. In addition, we simultaneously measured the responses of the magnetic, structural and electronic subsystems to the temperature- and field-induced martensitic transformation near Tcomp, showing an abnormal increase of hysteresis and consequently dissipation energy at cryogenic temperatures. Simultaneous measurements of magnetization and adiabatic temperature change ΔTad in pulsed magnetic fields reveal a change in sign of ΔTad and a substantial positive and irreversible ΔTad up to 15 K at 15 K as a consequence of increased dissipation losses and decreased heat capacity. Most importantly, this phenomenon is universal, it applies to any first-order material with non-negligible hysteresis and any stimulus, effectively limiting the utilization of their caloric effects for gas liquefaction at cryogenic temperatures.

Electric-field-induced phase transitions are the most important characteristics of antiferroelectric materials. However, in several prototype antiferroelectrics, these transitions are irreversible and the origin of this behavior is poorly understood. This prevents their widespread use, for example, in energy storage and memory applications. Here, we investigated the antiferroelectric-ferroelectric phase transitions in polycrystalline NaNbO3, a material recently suggested as the basis for lead-free antiferroelectrics with high energy storage densities. An irreversible transition from the antiferroelectric state to a new state showing macroscopic piezoelectricity (d33=35 pC/N) was induced at 11.6 kV/mm (room temperature, 1 Hz), accompanied by a 33% drop in permittivity. Microscopically, a change from a translational antiferroelectric domain structure to a wedge-shaped ferroelectric domain structure was observed using transmission electron microscopy. 23Na solid-state nuclear magnetic resonance allowed for a detailed study of the local structure and revealed pure antiferroelectric and coexisting antiferroelectric/ferroelectric nature of the samples before and after the application of an electric field, respectively. Interestingly, despite the large electric fields applied, only 50±5% of the material underwent the antiferroelectric-ferroelectric phase transition, which was related to the material´s microstructure. The temperature- and frequency-dependence of the phase transition was studied and compared to the behavior observed in lead-based antiferroelectric systems.

Owing to their large surface area, continuous conduction paths, high activity and pronounced anisotropy, nanowires are pivotal for a wide range of applications, yet far from thermodynamic equilibri...

In this work, the reduction of iron oxide γ-Fe2O3 nanoparticles by hydrogen at high pressures is studied. Increasing the hydrogen pressure enables reduction of γ-Fe2O3 to α-Fe at significantly lower temperatures. At low pressures, a temperature of 390 °C is necessary whereas at 530 bar complete reduction can be realized at temperatures as low as 210 °C. This leads to significant improvement in the final particle morphology, maintaining high surface-to-volume ratio of the nanoparticles with an average size of 47 ± 5 nm which is close to that of the precursor γ-Fe2O3. Neck formation, coalescence and growth during reduction can be significantly suppressed. Investigations of magnetic properties show that saturation magnetization of the reduced α-Fe nanoparticles decreases with particle size from 209 A m2 kg−1 at 390 °C reduction temperature to 204 A m2 kg−1 at 210 °C. Coercivity for the fine iron particles reaches 0.076 T which exceeds the theoretical anisotropy field. This is attributed to nano-scale surface effects.

Two-dimensional carbides/nitrides, typically called MXenes, are an emerging member of the ever-growing family of two-dimensional materials. The prediction of a ferromagnetic groundstate in chromium-containing MXenes has triggered growing interest in their chemical exfoliation from Cr-based MAX phases. However, the exfoliation poses serious difficulties using standard etching agents such as hydrofluoric acid (HF). Here, we investigate the exfoliability of Cr2GaC particles by chemical etching with aqueous HF both experimentally and theoretically. Structural and microstructural analyses show that the Cr2GaC particles decompose into chromium carbide and oxide without the formation of a Cr-based MXene. A thermodynamic analysis based on ab initio electronic structure calculations reveals that the exfoliation of Cr-based MXene from Cr2GaC by HF-etching is inhibited by more favorable competing reactions. This result confirms the experimental finding and suggests that HF is an unsuitable etching agent for a successful exfoliation of Cr2GaC.

Currently, anatase/rutile core/shell structures are accepted as highly efficient building blocks for TiO2-based catalysts or photoelectrodes used in dye-sensitized solar cells (DSSCs). It is unders...

Ferromagnetic Fe3Sn, Fe5Sn3 and Fe3Sn2 single crystals were synthesized using the reactive flux technique. Derived from single crystal x-ray diffraction and Transmission Electron Microscopy (TEM), a new structural model is proposed for the Fe5Sn3 crystals - the threefold twinning of an orthorhombic unit cell with (3 + 1) dimensional space group Pbcm(α00)0s0. The spontaneous magnetization (Ms) and the anisotropy constants K1 and K2 of Fe3Sn, Fe5Sn3 and Fe3Sn2 single crystals were determined in a wide temperature range using M(H) dependencies and a modified Sucksmith-Thompson technique. Ms and K1 were also evaluated in the framework of Density Functional Theory (DFT) and an overall good agreement was observed between the calculated and experimental results. Furthermore, a critical evaluation of different analytical models for the assessment of magnetocrystalline anisotropy was performed, which are restricted to the analysis of uniaxial magnetic domain patterns, and it is shown that such high-throughput techniques can lead to unrealistic results. Finally, a DFT high-throughput screening of the Fe-Sn phase diagram was used to identify Fe-Sn based phases with potential to be stabilized upon alloying, and their magnetization and magnetocrystalline anisotropy were evaluated. The results show that a similar strong anisotropy as observed in Fe3Sn may also be found in other Fe-Sn based phases, having higher potential to be used as hard magnetic material.

Permanent magnets based on neodymium-iron-boron (Nd-Fe-B) alloys provide the highest performance and energy density, finding usage in many high-tech applications. Their magnetic performance relies on the intrinsic properties of the hard-magnetic Nd$_2$Fe$_{14}$B phase combined with control over the microstructure during production. In this study, a novel magnetic hardening mechanism is described in such materials based on a solid-state phase transformation. Using modified Nd-Fe-B alloys of the type Nd$_{16}$Fe$_{bal-x-y-z}$Co$_x$Mo$_y$Cu$_z$B$_7$ for the first time it is revealed how the microstructural transformation from the metastable Nd$_2$Fe$_{17}$B$_x$ phase to the hard-magnetic Nd$_2$Fe$_{14}$B phase can be thermally controlled, leading to an astonishing increase in coercivity from ≈200 kAm$^{−1}$ to almost 700 kAm$^{−1}$. Furthermore, after thermally treating a quenched sample of Nd$_{16}$Fe$_{56}$Co$_{20}$Mo$_2$Cu$_2$B$_7$, the presence of Mo leads to the formation of fine FeMo$_2$B$_2$ precipitates, in the range from micrometers down to a few nanometers. These precipitates are responsible for the refinement of the Nd$_2$Fe$_{14}$B grains and so for the high coercivity. This mechanism can be incorporated into existing manufacturing processes and can prove to be applicable to novel fabrication routes for Nd-Fe-B magnets, such as additive manufacturing

An antipolar phase is confirmed for NaNbO3 thin films grown by pulsed laser deposition on SrTiO3 (100) substrates. Reciprocal space maps and transmission electron microscopy reveal the presence of characteristic 1/4 superlattice reflections, indicative of the antipolar displacement of Na and Nb-ions. Furthermore, x-ray diffraction unveils the presence of two different orientations of the same phase for thin films beyond a critical thickness of about 60 nm. This orientation change with increasing thickness can be explained as an extraordinary strain compensation mechanism, changing magnitude and sign of the strain at the same time. The polarization vs electric field behavior exposes a characteristic thickness dependence, with the antiferroelectric phase stabilized for very thin films and a field induced ferroelectric hysteresis for a film of 310 nm having a maximum polarization of 26.5 μC [Formula: see text], which is among the highest values reported for NaNbO3 thin films grown on SrTiO3 (100).

Many nanofabrication processes require sophisticated equipment, elevated temperature, vacuum or specific atmospheric conditions, templates, and exotic chemicals, which severely hamper their implementation in real-world applications. In this study, we outline a fully wet-chemical procedure for equipping a 3D carbon felt (CF) substrate with a multifunctional, titania nanospike-supported Pt-Pd nanoparticle (Pt-Pd-TiO2@CF) layer in a facile and scalable manner. The nanostructure, composition, chemical speciation, and formation of the material was meticulously investigated, evidencing the conformal coating of the substrate with a roughened layer of nanocrystalline rutile spikes by chemical bath deposition from Ti3+ solutions. The spikes are densely covered by bimetallic nanoparticles of 4.4 ± 1.1 nm in size, which were produced by autocatalytic Pt deposition onto Pd seeds introduced by Sn2+ ionic layer adsorption and reaction. The as-synthesized nanocomposite was applied to the (photo)electro-oxidation of formic acid (FA), exhibiting a superior performance compared to Pt-plated, Pd-seeded CF (Pt-Pd@CF) and commercial Pt-C, indicating the promoting electrocatalytic role of the TiO2 support. Upon UV-Vis illumination, the performance of the Pt-Pd-TiO2@CF electrode is remarkably increased (22-fold), generating a current density of 110 mA cm-2, distinctly outperforming titania-free Pt-Pd@CF (5 mA cm-2) and commercial Pt-C (6 mA cm-2) reference catalysts. In addition, the Pt-Pd-TiO2@CF showed a much better stability, characterized by a very high poisoning tolerance for in situ-generated CO intermediates, whose formation is hindered in the presence of TiO2. This overall performance boost is attributed to a dual enhancement mechanism (∼30% electrocatalytic and ∼70% photoelectrocatalytic). The photogenerated electrons from the TiO2 conduction band enrich the electron density of the Pt nanoparticles, promoting the generation of active oxygen species on their surfaces from adsorbed oxygen and water molecules, which facilitate the direct FA electro-oxidation into CO2.

The potential of thermoelectric thin films lies in wide range of applications from micro-energy harvesting to the sensors. For this, it is essential to have high power factor and ultra-low thermal conductivity which have been reported in thin films produced by expensive vacuum techniques. However, for practical applications, it is essential to use inexpensive technique to grow thin film in large area. In this direction, we report the use of mist-chemical vapor deposition (CVD) technique to develop oxide thin films for thermoelectric application. We grow c-axis oriented nano-porous thin films of 2% Al-doped ZnO (AZO). These nano-porous films have enhance phonon scattering which results in the depression of thermal conductivity (κ) while maintaining similar order of magnitude of power factor as reported in dense films prepared by vacuum techniques. For example, κ300K decreases from 6.5 W/m.K for dense thin film (porosity = 7.9%) grown by pulsed laser deposition to 5.54 W/m.K for porous film (porosity = 24.2%) grown by mist-CVD while maintaining the power factor of similar order of magnitude for AZO film deposited on SrTiO3. The depression of thermal conductivity in porous films may lead to higher figure of merit which is promising for practical applications of thermoelectric oxide films.

Nano-objects are favored structures for applications such as catalysis and sensing. Although they already provide a large surface-to-volume ratio, this ratio can be further increased by shape-selective plating of the nanostructure surfaces. This process combines the conformity of autocatalytic deposition with the defined nucleation and growth characteristics of colloidal nanoparticle syntheses. However, many aspects of such reactions are still not fully understood. In this study, we investigate in detail the growth of spiky nickel nanotubes in polycarbonate template membranes. One distinctive feature of our synthesis is the simultaneous growth of nanospikes on both the inside and outside of nanotubes while the tubes are still embedded in the polymer. This is achieved by combining the plating process with locally enhanced in situ etching of the poylmer template, for which we propose a theory. Electron microscopy investigations reveal twinning defects as the driving force for the growth of crystalline nanospikes. Deposit crystallinity is ensured by the reducing agent hydrazine. Iminodiacetic acid is not only used as a complexing agent during synthesis but apparently also acts as a capping agent and limits random nucleation on the spike facets. Finally, we apply our synthesis to templates with interconnected pores to obtain free-standing spiky nickel nanotube networks, demonstrating its ability to homogeneously coat substrates with extended inner surfaces and to operate in nanoscale confinement.

To facilitate the implementation of biosensors based on the localized surface plasmon resonance (LSPR) of metal nanostructures, there is a great need for cost-efficient, flexible, and tunable methods for producing plasmonic coatings. Due to its simplicity and excellent conformity, electroless plating (EP) is well suited for this task. However, it is traditionally optimized to produce continuous metal films, which cannot be employed in LSPR sensors. Here, we outline the development of an EP strategy for depositing island-like silver nanoparticle (NP) films on glass with distinct LSPR bands. The fully wet-chemical process only employs standard chemicals and proceeds within minutes at room temperature. The key step for producing spread-out NP films is an accelerated ripening of the silver seed layer in diluted hydrochloric acid, which reduces the nucleation density during plating. The reaction kinetics and mechanisms are investigated with scanning (transmission) electron microscopy (SEM/STEM), X-ray photoelectron spectroscopy (XPS), and UV-vis spectroscopy, with the latter enabling a convenient live monitoring of the deposition, allowing its termination at a stage of desired optical properties. The sensing capabilities of chemically deposited NP films as LSPR transducers are exemplified in DNA biosensing. To this end, a sensing interface is prepared using layer-by-layer (LbL) buildup of polyelectrolytes (PE), followed by adsorption and covalent immobilization of ssDNA. The obtained LSPR transducers demonstrate robustness and selectivity in sensing experiments with binding complementary and unrelated DNA strands.

MAX phases are typically prepared by high-temperature (oftentimes high-pressure) solid-state methods. Here, we report a new wet chemistry based synthesis technique starting from an aqueous solution of metal nitrates and citric acid to prepare MAX phase Cr2GaC. This solution-processable precursor mixture has the potential to be easily scaled, painted, printed or fabricated onto supports – an advantage that is demonstrated by the formation of hollow carbon microspheres which are decorated with Cr2GaC particles. A small amount of chromium carbide and oxide remains in the product, however, the amount of the latter can be reduced by a larger excess in citric acid in the precursor gel. The transformation mechanism of the initial amorphous gel into highly crystalline and anisotropic MAX phase particles is investigated by detailed thermal analysis. Transmission electron microscopy studies are conducted to elucidate the microstructure of the sol–gel-prepared particles as well as the decorated hollow microspheres. From magnetic susceptibility measurements, the density of states at the Fermi level is deduced reflecting the quality of the Pauli paramagnet Cr2GaC.

Ni-Mn-based metamagnetic shape-memory alloys exhibit a giant thermal response to magnetic fields and uniaxial stress which can be utilized in single caloric or multicaloric cooling concepts for energy-efficient and sustainable refrigeration. However, during cyclic operation these alloys suffer from structural and functional fatigue as a result of their high intrinsic brittleness. Here, we present based on Fe-doping of Ni-Mn-In a microstructure design strategy which simultaneously improves cyclic stability and maintains the excellent magnetocaloric and elastocaloric properties. Our results reveal that precipitation of a strongly Fe-enriched and In-depleted coherent secondary gamma-phase at grain boundaries can ensure excellent mechanical stability by hindering intergranular fracture during cyclic loading. In this way, a large elastocaloric effect of -4.5 K was achieved for more than 16000 cycles without structural or functional degradation, which corresponds to an increase of the cyclic stability by more than three orders of magnitude as compared to single-phase Ni-Mn-In-(Fe). In addition, we demonstrate that the large magnetocaloric effect of single-phase Ni-Mn-In-(Fe) can be preserved in the dual-phase material when the secondary gamma-phase is exclusively formed at grain boundaries as the martensitic transformation within the Heusler matrix is barely affected. This way, an adiabatic temperature change of -3 K and an isothermal entropy change of 15 $Jkg^{-1}K^{-1}$ was obtained in 2 T for dual-phase Ni-Mn-In-Fe. We expect that this concept can be applied to other single caloric and mutlicaloric materials, therewith paving the way for solid-state caloric cooling applications.

Microstructure design allows to prevent intergranular cracking and premature failure in Co–Ni–Ga shape memory alloys. Favorable grain boundary configurations are established using additive manufacturing techniques, namely, direct energy deposition (DED) and laser powder bed fusion (L-PBF). L-PBF allows to establish a columnar grain structure. In the Co–Ni–Ga alloy processed by DED, a microstructure with strong ⟨001⟩ texture is obtained. In line with optimized microstructures, the general transformation behavior is essential for performance. Transition parameters such as transition temperature and thermal hysteresis depend on chemical composition, homogeneity, and presence of precipitates. However, these parameters are highly dependent on the processing method used. Herein, the first-order magnetostructural transformation and magnetization properties of Co–Ni–Ga processed by DED and L-PBF are compared with single-crystalline and as-cast material. In the alloy processed by L-PBF, Ga evaporation and extensive formation of the ferromagnetic Co-rich γ'-phase are observed, promoting a very wide transformation range and large thermal hysteresis. In comparison, following DED, the material is characterized by minor chemical inhomogeneity and transition and magnetization behavior being similar to that of a single crystal. This clearly renders DED-processed Co–Ni–Ga to become a promising candidate material for future shape memory applications. © 2022 The Authors. Advanced Engineering Materials published by Wiley-VCH GmbH.

Low-frequency noise in Y2O3-based resistive random-access memory devices with analog switching is studied at intermediate resistive states and as a function of dc cycling. A universal 1/f(alpha)-type behavior is found, with a frequency exponent of alpha approximate to 1.2 that is independent of the applied reset voltage or the device resistance and is attributed to the intrinsic abundance of oxygen vacancies unique to the structure of yttria. Remarkably, the noise magnitude in the high resistive state systematically decreases through dc training. This effect is attributed to the stabilization of the conductive filament via the consumption of oxygen vacancies, thus reducing the number of active fluctuators in the vicinity of the filament.

In this study, molecular beam epitaxy is utilized to stabilize a nanostructured thin-film magnet consisting of a soft magnetic Y2Co17 exchange coupled to hard magnetic YCo5. While, typically, a phase decomposition can be obtained in rare-earth cobalt systems only by the addition of further elements like Cu, Fe, and Zr and complex heat treatments, here we directly induce phase separation by growth kinetics. The resulting nanoscale architecture, as revealed by cross-sectional transmission electron microscopy, is composed of a network of coherently interlinked and aligned Y2Co17 and YCo5 building blocks. The formation of coherent precipitations is facilitated by the perfectly matching lattice constants, atomic species, and crystal symmetry of the two phases with vastly different magnetocrystalline anisotropies. The hard magnetic phase induces an aligned uniaxial anisotropy in Y2Co17, resulting in substantial coercivity associated with enhanced energy products. This work highlights the importance of thin-film epitaxy in understanding magnetic hardening mechanisms and suggests strategies for a rational design of future sustainable magnetic systems.