Magnetic and mechanical hardening of nano-lamellar magnets using thermo-magnetic fields.

High-performance magnetic materials based on rare-earth intermetallic compounds are critical for energy conversion technologies. However, the high cost and supply risks of rare-earth elements necessitate the development of affordable alternatives. Another challenge lies in the inherent brittleness of current magnets, which limits their applications for high dynamic mechanical loading conditions during service and complex shape design during manufacturing towards high efficiency and sustainability.

Voltage-Gated 90° Switching of Bulk Perpendicular Magnetic Anisotropy in Ferrimagnets.

Unraveling the mechanism behind bulk perpendicular magnetic anisotropy (PMA) in amorphous rare earth-transition metal films has proven challenging. This is largely due to the inherent complexity of the amorphous structure and the entangled potential origins arising from microstructure and atomic structure factors. Here, we present an approach wherein the magneto-electric effect is harnessed to induce 90° switching of bulk PMA in Tb-Co films to in-plane directions by applying voltages of only -1.

ULtimate MAGnetic characterization (ULMAG) at the ID12 beamline of ESRF: from element-specific properties to macroscopic functionalities.

We present a novel instrument designed for advanced magnetic study, installed at the ID12 beamline of the European Synchrotron Radiation Facility in Grenoble, France. This instrument offers the unique capability to simultaneously measure element-specific microscopic and macroscopic properties related to the magnetic, electronic and structural characteristics of materials. In addition to X-ray absorption, X-ray magnetic circular dichroism alongside X-ray diffraction patterns, the macroscopic magnetization, volume changes, caloric properties and electrical resistivity of magnetic materials could be measured strictly under the same experimental conditions as a function of both magnetic field (up to ±7 T) and temperature (ranging from 2.

Stable Operation of Copper-Protected La(FeMnSi)H Regenerators in a Magnetic Cooling Unit.

Magnetic refrigeration leads the current commercialization efforts of ambient caloric cooling technologies, is considered among its peers most promising in terms of anticipated energy efficiency gain, and allows for complete elimination of harmful coolants. By now, functional magnetocaloric components (so-called regenerators) based on Mn-substituted and hydrogenated LaFeSi alloys are commercially available. However, this alloy system exhibits magnetostriction, is susceptible to fracture, oxidation, and does not passivate well, rendering it prone to failure and corrosion, particularly when using water as favorable heat exchange medium.

Two-gigapascal-strong ductile soft magnets.

Soft magnetic materials (SMMs) are indispensable for electromechanical energy conversion in high-efficiency applications, but they are exposed to increasing mechanical loading conditions in electric motors due to higher rotational speeds. Enhancing the yield strength of SMMs is essential to prevent the degradation in magnetic performance and failure from plastic deformation, yet most SMMs have yield strengths far below one gigapascal. Here, we present a multicomponent nanostructuring strategy that doubles the yield strength of SMMs while maintaining ductility.

Residual Ferromagnetic Regions Affecting the First-Order Phase Transition in Off-Stoichiometric Fe-Rh.

Among the magnetocaloric materials featuring first-order phase transitions (FOPT), FeRh is considered as a reference system to study the FOPT because it is a "simple" binary system with a CsCl structure exhibiting a large adiabatic temperature change. Recently, ab initio theory predicted that changes in the Fe/Rh stoichiometry in the vicinity of equiatomic composition strongly influence the FOPT characteristics. However, this theoretical prediction was not clearly verified experimentally.

Boosting Coercivity of 3D Printed Hard Magnets through Nano-Modification of the Powder Feedstock.

The demand for strong, compact permanent magnets essential for the energy transition drives innovation in magnet manufacturing. Additive manufacturing, particularly Powder Bed Fusion of metals using a laser beam (PBF-LB/M), offers potential for near-net-shaped Nd-Fe-B permanent magnets but often falls short compared to conventional methods. A less explored strategy to enhance these magnets is feedstock modification with nanoparticles.

Giant magnetocaloric effect in a rare-earth-free layered coordination polymer at liquid hydrogen temperatures.

Magnetic refrigeration, which utilizes the magnetocaloric effect, can provide a viable alternative to the ubiquitous vapor compression or Joule-Thompson expansion methods of refrigeration. For applications such as hydrogen gas liquefaction, the development of magnetocaloric materials that perform well in moderate magnetic fields without using rare-earth elements is highly desirable. Here we present a thorough investigation of the structural and magnetocaloric properties of a novel layered organic-inorganic hybrid coordination polymer Co(OH)(SO)[enH] (enH = ethylenediammonium).

Green Ironmaking at Higher H Pressure: Reduction Kinetics and Microstructure Formation During Hydrogen-Based Direct Reduction of Hematite Pellets.

Hydrogen-based direct reduction (HyDR) of iron ores has attracted immense attention and is considered a forerunner technology for sustainable ironmaking. It has a high potential to mitigate CO emissions in the steel industry, which accounts today for ~ 8-10% of all global CO emissions. Direct reduction produces highly porous sponge iron via natural-gas-based or gasified-coal-based reducing agents that contain hydrogen and organic molecules.

High-Throughput Screening of All--Metal Heusler Alloys for Magnetocaloric Applications.

Due to their versatile composition and customizable properties, ABC Heusler alloys have found applications in magnetic refrigeration, magnetic shape memory effects, permanent magnets, and spintronic devices. The discovery of all--metal Heusler alloys with improved mechanical properties compared to those containing main group elements presents an opportunity to engineer Heusler alloys for energy-related applications. Using high-throughput density-functional theory calculations, we screened magnetic all--metal Heusler compounds and identified 686 (meta)stable compounds.

Multicaloric Cryocooling Using Heavy Rare-Earth Free La(Fe,Si)-Based Compounds.

The transition toward a carbon-neutral society based on renewable energies goes hand in hand with the availability of energy-efficient technologies. Magnetocaloric cooling is a very promising refrigeration technology to fulfill this role regarding cryogenic gas liquefaction. However, the current reliance on highly resource critical, heavy rare-earth-based compounds as magnetocaloric material makes global usage unsustainable.

Bulk Nanostructured Silicide Thermoelectric Materials by Reversible Hydrogen Absorption-Desorption.

The production of bulk nanostructured silicide thermoelectric materials by a reversible hydrogen absorption-desorption process is demonstrated. Here, high-pressure reactive milling under 100 bar hydrogen is used to decompose the CaSi phase into CaH and Si. Subsequent vacuum heat treatment results in hydrogen desorption and recombination of the constituents into the original phase.

Strong and ductile high temperature soft magnets through Widmanstätten precipitates.

Fast growth of sustainable energy production requires massive electrification of transport, industry and households, with electrical motors as key components. These need soft magnets with high saturation magnetization, mechanical strength, and thermal stability to operate efficiently and safely. Reconciling these properties in one material is challenging because thermally-stable microstructures for strength increase conflict with magnetic performance.

Surfactant-driven optimization of iron-based nanoparticle synthesis: a study on magnetic hyperthermia and endothelial cell uptake.

This work examines the effect of changing the ratio of different surfactants in single-core iron-based nanoparticles with respect to their specific absorption rate in the context of magnetic hyperthermia and cellular uptake by human umbilical vein endothelial cells (HUVEC). Three types of magnetic nanoparticles were synthesized by separately adding oleic acid or oleylamine or a mixture of both (oleic acid/oleylamine) as surfactants. A carefully controlled thermal decomposition synthesis process led to monodispersed nanoparticles with a narrow size distribution.

Life Cycle Assessment of Rare Earth Elements-Free Permanent Magnet Alternatives: Sintered Ferrite and Mn-Al-C.

Permanent magnets are fundamental constituents in key sectors such as energy and transport, but also robotics, automatization, medicine, etc. High-performance magnets are based on rare earth elements (RE), included in the European list of critical raw materials list. The volatility of their market increased the research over the past decade to develop RE-free magnets to fill the large performance/cost gap existing between ferrites and RE-based magnets.

A Machine Learning Framework for Quantifying Chemical Segregation and Microstructural Features in Atom Probe Tomography Data.

Atom probe tomography (APT) is ideally suited to characterize and understand the interplay of segregation and microstructure in modern multi-component materials. Yet, the quantitative analysis typically relies on human expertise to define regions of interest. We introduce a computationally efficient, multi-stage machine learning strategy to identify compositionally distinct domains in a semi-automated way, and subsequently quantify their geometric and compositional characteristics.

Giant Magnetocaloric Effect in Magnets Down to the Monolayer Limit.

2D magnets can potentially revolutionize information technology, but their potential application to cooling technology and magnetocaloric effect (MCE) in a material down to the monolayer limit remain unexplored. Herein, it is revealed through multiscale calculations the existence of giant MCE and its strain tunability in monolayer magnets such as CrX (X = F, Cl, Br, I), CrAX (A = O, S, Se; X = F, Cl, Br, I), and Fe GeTe . The maximum adiabatic temperature change ( ), maximum isothermal magnetic entropy change, and specific cooling power in monolayer CrF are found as high as 11 K, 35 µJ m  K , and 3.

High-Throughput Design of Magnetocaloric Materials for Energy Applications: MM´X alloys.

Magnetic refrigeration offers an energy efficient and environmental friendly alternative to conventional vapor-cooling. However, its adoption depends on materials with tailored magnetic and structural properties. Here a high-throughput computational workflow for the design of magnetocaloric materials is introduced.

Machine learning-enabled high-entropy alloy discovery.

High-entropy alloys are solid solutions of multiple principal elements that are capable of reaching composition and property regimes inaccessible for dilute materials. Discovering those with valuable properties, however, too often relies on serendipity, because thermodynamic alloy design rules alone often fail in high-dimensional composition spaces. We propose an active learning strategy to accelerate the design of high-entropy Invar alloys in a practically infinite compositional space based on very sparse data.

A mechanically strong and ductile soft magnet with extremely low coercivity.

Soft magnetic materials (SMMs) serve in electrical applications and sustainable energy supply, allowing magnetic flux variation in response to changes in applied magnetic field, at low energy loss. The electrification of transport, households and manufacturing leads to an increase in energy consumption owing to hysteresis losses. Therefore, minimizing coercivity, which scales these losses, is crucial.

Ultrastrong and Ductile Soft Magnetic High-Entropy Alloys via Coherent Ordered Nanoprecipitates.

The lack of strength and damage tolerance can limit the applications of conventional soft magnetic materials (SMMs), particularly in mechanically loaded functional devices. Therefore, strengthening and toughening of SMMs is critically important. However, conventional strengthening concepts usually significantly deteriorate soft magnetic properties, due to Bloch wall interactions with the defects used for hardening.

Alloying effect on the order-disorder transformation in tetragonal FeNi.

Tetragonal ([Formula: see text]) FeNi is a promising material for high-performance rare-earth-free permanent magnets. Pure tetragonal FeNi is very difficult to synthesize due to its low chemical order-disorder transition temperature ([Formula: see text] K), and thus one must consider alternative non-equilibrium processing routes and alloy design strategies that make the formation of tetragonal FeNi feasible. In this paper, we investigate by density functional theory as implemented in the exact muffin-tin orbitals method whether alloying FeNi with a suitable element can have a positive impact on the phase formation and ordering properties while largely maintaining its attractive intrinsic magnetic properties.

Magnetoelectric Tuning of Pinning-Type Permanent Magnets through Atomic-Scale Engineering of Grain Boundaries.

Pinning-type magnets with high coercivity at high temperatures are at the core of thriving clean-energy technologies. Among these, Sm Co -based magnets are excellent candidates owing to their high-temperature stability. However, despite intensive efforts to optimize the intragranular microstructure, the coercivity currently only reaches 20-30% of the theoretical limits.

Giant voltage-induced modification of magnetism in micron-scale ferromagnetic metals by hydrogen charging.

Owing to electric-field screening, the modification of magnetic properties in ferromagnetic metals by applying small voltages is restricted to a few atomic layers at the surface of metals. Bulk metallic systems usually do not exhibit any magneto-electric effect. Here, we report that the magnetic properties of micron-scale ferromagnetic metals can be modulated substantially through electrochemically-controlled insertion and extraction of hydrogen atoms in metal structure.

Production of Fe nanoparticles from γ-FeO by high-pressure hydrogen reduction.

In this work, the reduction of iron oxide γ-FeO nanoparticles by hydrogen at high pressures is studied. Increasing the hydrogen pressure enables reduction of γ-FeO 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.