Recently, the 4d transition-metal oxide RuO2 has attracted significant interest as a candidate altermagnet. However, its magnetic ground state remains controversial, as spin-transport signatures of spin-splitting torque conflict with spectroscopic evidence regarding long-range magnetic order. Using exchange bias as a local probe, we show that antiferromagnetism in RuO2 is very fragile but can be stabilized by the presence of oxygen vacancies (Vo). In epitaxial RuO2(t)/La0.5Sr0.5CoO3 bilayers, the exchange bias field exhibits an anomalous monotonic rise with the decrease of RuO2 thickness, while x-ray absorption spectra reveal the concurrent reduction in Ru valence state (i.e., increasing in Vo content) toward the interface. Further oxygen annealing has almost extinguished the exchange bias effect in all samples, directly linking the Vo density to the antiferromagnetism strength of RuO2. Density-functional calculations confirm that oxygen vacancies, regardless of crystallographic site, enlarge the antiferromagnetism-to-paramagnetism energy difference by up to one order of magnitude, and thus stabilize the antiferromagnetic state of RuO2. These results reconcile prior disparate reports, establishing vacancies as the dominant control parameter for RuO2 magnetism, and providing a practical route for engineering robust altermagnetic order in RuO2 thin-film devices.

Current-induced spin-orbit torque (SOT) offers a promising approach for manipulating perpendicular magnetization in spintronic devices, enabling low-power and ultrafast applications. However, deterministic SOT switching typically requires an external in-plane magnetic field to break symmetry, complicating high-density device integration. Here, we demonstrate field-free SOT switching in the perpendicular ferrimagnet CoGd by inducting tilted magnetic anisotropy (TMA) via thermal annealing under an inplane magnetic field. The TMA's tilt angle is tunable by adjusting the annealing field strength, allowing deterministic switching when the in-plane TMA component aligns with the spin-polarization direction. This method leverages the low stray field, ultrafast spin dynamics, and high operation frequencies of ferrimagnet, offering a scalable solution for advanced spintronic devices.

Merely enhancing the electromagnetic absorption capability of microwave-absorbing materials has proven insufficient for their practical applications in complicated environments such as military and aerospace fields. Consequently, materials that integrate outstanding comprehensive performance with thermal insulation stability are highly favored. In this study, the porous NiFe2O4@BaTiO3 composites were prepared through a synergistic process that combines freeze-drying with high-temperature annealing. The electromagnetic parameters were judiciously tuned by systematically adjusting the loading amount of BaTiO3. Benefiting from the cooperative electromagnetic loss and optimized impedance matching, the samples filled with 50 % BaTiO3 (NiFe2O4@Ba-TiO3-50 %) manifest the most superior electromagnetic wave absorption (EWA) performance, with an effective absorption bandwidth (EAB) of 6.75 GHz and a minimal reflection loss (RLmin) of-45.74 dB. Furthermore, radar cross section (RCS) simulations reveal an exceptional radar scattering reduction capability, making a significant contribution to practical stealth applications. Additionally, NiFe2O4@BaTiO3-50 % can withstand 1100 degrees C for 25 min and reduce the temperature by nearly 900 degrees C, which exhibit pronounced thermal resistance and thermal mechanical stability. This work pioneers a novel approach for radar stealth materials in high-temperature environments, demonstrating significant application potential in radar stealth, thermal insulation, and advanced military fields.

Polycrystalline RCr0.3Ge2 (R = Ho, Er) compounds exhibiting magnetic transitions in the liquid helium temperature region were successfully synthesized, and their magnetic properties and magnetocaloric effects (MCEs) were systematically investigated. Both compounds exhibit antiferromagnetic ordering with N & eacute;el temperature (T-N) of 7.3 and 3.4 K, respectively. Notably, HoCr0.3Ge2 and ErCr0.3Ge2 compounds demonstrate large reversible MCEs characterized by negligible thermal and magnetic hysteresis. Under a magnetic field change of 0-5 T, the maximum magnetic entropy changes [(-Delta S-M)(max)] reach 9.0 and 9.9 J/kg K for HoCr0.3Ge2 and ErCr0.3Ge2 compounds, respectively, accompanied by considerable refrigeration capacities of 118.1 and 111.0 J/kg. The combination of significant MCE performance and excellent reversibility near 4.2 K positions these materials as highly promising candidates for practical cryogenic magnetic refrigeration.

This study reveals the critical role of cooling rate (20-103 K/h) in regulating Co2+ occupancy distribution and magnetic anisotropy in La-Co co-substituted M-type strontium ferrites (Sr0.7La0.3Fe11.5Co0.3O19). The combined analysis of neutron diffraction, Raman spectroscopy, and magnetic characterization demonstrates that slow cooling (20 K/h) promotes 62.7% of Co2+ to occupy the anisotropy-enhancing 4f1 tetrahedral site, increasing the anisotropy field (HA=26.0 kOe) compared to the common furnace cooling (HA=24.8 kOe). In contrast, rapid cooling (103 K/h) reduces 4f1 occupancy to 53.7%, consequently decreasing HA. A "freezing temperature" (Teq) model quantitatively correlates cooling rate with Co2+ site preference, confirming that slower cooling enhances thermodynamic equilibrium. This work provides a kinetic pathway to tailor the fundamental properties beyond compositional design.

Sm-Co co-doped NiCuZn ferrites (Ni0.6–xCu0.05Zn0.35CoxSm0.02Fe1.98O4, x = 0.01, 0.02, 0.03, 0.035, 0.04, 0.05) were prepared using the conventional solid-state reaction method. With a fixed Sm3+ doping concentration, the effects of Co2+ content on the phase composition, microstructure, gyromagnetic and dielectric properties were systematically investigated. All samples exhibit a coexistence of spinel and SmFeO3 secondary phase, along with dense and uniform grain structure. The saturation magnetization first decreases and then increases with increasing Co2+ content, reaching a minimum at x = 0.03. The magnetocrystalline anisotropy constant K1 increases from –4.31 kJ/m3 to 5.32 kJ/m3 as the Co2+ content rises. It changes from negative to positive at x = 0.035, indicating near-zero anisotropy. Sm3+ doping refines the grain size and suppresses Fe2+/Fe3+ electron hopping. This reduces the dielectric loss by approximately one order of magnitude. The optimized composition (x = 0.035) achieves a combination of high saturation magnetization (5027 Gs), low dielectric loss (3.51×10–4), narrow ferromagnetic resonance linewidth (97.5 Oe), and high Curie temperature (374 °C). This study demonstrates that the Sm-Co co-doping strategy provides an effective route for developing polycrystalline NiCuZn ferrites with both high magnetic moment and low loss.

The Shastry-Sutherland lattice is a prototypical frustrated quantum magnet. It is notable for its exactly solvable dimer-singlet ground state and hosts a wealth of magnetic phenomena under external fields. Here, this work investigates the high-spin (S = 7/2) Eu-based magnet Eu2MgSi2O7 (EMSO) using low-temperature magnetothermal measurements and Monte Carlo simulations, revealing a giant magnetocaloric effect (MCE) in this Shastry-Sutherland compound. The entropy change peak value is found to be 55.0 J kg-1 K-1 under a field change of B = 0-4 T, approximately 1.5 times larger than the commercial Gd3Ga5O12 (GGG). Adiabatic demagnetization refrigeration achieves a lowest temperature of 151 mK, deeply into the sub-Kelvin regime. Furthermore, a distinctive cooling effect persists below about 1 T, a characteristic absent for conventional magnetic coolants. A dipolar Shastry-Sutherland model is introduced as a minimal model to describe this system; in particular, the experimentally revealed 1/3 magnetization pseudo-plateau can be ascribed to the presence of dipolar couplings between Eu2+ ions, further stabilized by the thermal fluctuations, explaining the persistent cooling effect. This work establishes EMSO as a novel platform for exploring the dipolar Shastry-Sutherland system and for sub-Kelvin adiabatic demagnetization refrigeration.

Fe-based nanocrystalline powders are ideal soft magnetic materials for matching the wide bandgap semiconductors. Previously developed Fe-based nanocrystalline alloys are difficult to produce high-quality precursor powder by gas atomization due to their poor amorphous forming ability, and their following nanocrystallizations also require high temperatures or heating rates. In present work, we invented novel high-performance Fe-based nanocrystalline powders that can be directly manufactured by gas atomization without annealing. The as-atomized Fe73.3Si12B13Cu1.7 nanocrystalline powders exhibit fine alpha-Fe(Si) crystals with an average size of 15.1 nm and high saturation magnetization ( Ms ) of 156.2 emu/g. The Fe73.3Si12B13Cu1.7 soft magnetic powder cores annealed at 480 degrees C for 60 min process high effective permeability of 35.9 and low core losses (50 mT/100 kHz) of 310.1 mW/cm3. These outstanding magnetic properties and good processability make the developed Fe73.3Si12B13Cu1.7 nanocrystalline powders highly promising for high-performance inductors and transformers. (c) 2025 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Achieving high coercivity without sacrificing ultra-high remanence is challenging for grain boundary diffusion (GBD) treated Nd-Fe-B magnets, as the lean grain boundary phase (GBs) in high-remanence compositions limits diffusion efficiency. Herein, low-cost NdH2 is employed to compensate for the GBs and enhance Tb diffusion. Low-Nd-content magnets were coated with TbH2 and NdH2 and subjected to GBD, yielding a magnet with remanence of 14.51 kGs and coercivity of 20.67 kOe, outperforming the TbH2-only diffused counterpart. NdH2 replenishment increases the grain boundary fraction, expands diffusion channels, and extends Tb penetration depth by 60%. Crucially, a continuous Tb-rich shell forms around main-phase grains. In-situ Lorentz TEM reveals that this intact shell shifts domain nucleation from grain edges to the interior and hinders domain wall propagation at the core–shell interface. Micromagnetic simulations confirm that shell integrity, especially on the plane perpendicular to the c-axis, is vital for coercivity enhancement. This work offers a simple route to high-remanence magnets with improved coercivity, showing application potential in miniaturized devices and high-temperature environments.

With the increasing requirements of electromagnetic wave (EMW) absorption, developing EMW absorbers with high-efficiency anti-corrosion performance which can be effectively applied in extreme corrosive environments is imperative and constitutes a hot issue in the current research. Herein, based on the composition modulation of ZrO2 and SiO2 layer, the dual-oxides confined carbonyl iron (CI@ZrO2/SiO2) composite displays a minimum reflection loss (RLmin) of-48.58 dB@1.9 mm and an effective absorption bandwidth (EAB) of 7.62 GHz@1.6 mm. Besides, the CI@ZrO2/SiO2 displays superior corrosion resistance with corrosion current density (icorr) of 8.62 x 10-7A/cm2 and polarization resistance (Rp) of 3.64x105 Omega. This work proposes a strategy to optimize the broadband EMW absorption properties as well as the mass production toward the corrosion resistance applications.

To meet the growing demand for structurally integrated microwave absorbers that combine robust load-bearing capacity with broadband and oblique-incidence absorption, this work designs and fabricates a bio-inspired composite featuring a hierarchical porous architecture. Drawing inspiration from the fiber-reinforced, periodically arrayed microstructure of the weevil beetle shell, the triply periodic minimal surface (TPMS)-based topological structures are additively manufactured using short-cut carbon fiber-reinforced polyamide (SCF/PA). Among the TPMS architectures evaluated, the primitive shell-type structure was selected for its optimal balance of broadband absorption and mechanical robustness, achieving a reflection loss (RL) of − 59.65 dB at 13.23 GHz and an effective absorption bandwidth (EAB, RL ≤ − 10 dB) of 30.04 GHz at a thickness of 24.7 mm, in addition to a flexural strength of 13.81 ± 1.20 MPa. A sandwich composite was then fabricated by laminating glass fiber and carbon fiber fabrics onto the TPMS core. This composite exhibits a flexural strength of 34.16 ± 0.64 MPa with a density of 0.36 g/cm3, while maintaining an EAB of 30.92 GHz and an RL of − 36.61 dB at 12.78 GHz (25.72 mm). Under oblique incidence, it retains 75.6

Achieving multistep magnetization switching in two-dimensional (2D) ferrimagnets demonstrates substantial promise for advancing high-density non-Boolean logic and memory devices. However, existing 2D ferrimagnets are still hampered by low Curie temperatures and a lack of tunable multiple magnetic states. Here, we report the successful synthesis of a family of 2D Fe0.875S(1-x)Sex alloy with robust room-temperature ferrimagnetism. The key magnetic and electrical properties can be effectively regulated by tailoring the chalcogen ratio in Fe0.875S(1-x)Sex alloy. Notably, multiple magnetic states and resistance plateaus are observed because of the spin canting behavior, enabling the realization of several distinct spin states by adjusting magnetic fields and temperatures, thereby demonstrating great potential for multistate applications. Density functional theory calculations further reveal that the evolution of magnetic anisotropy originates from variations in the orbital occupation of electronic states near the Fermi level. Our work can expand the library of 2D metallic ferrimagnets and pave the way for designing high-density spintronic devices.

Reducing the dependence on Nd while preserving high magnetic performance is a key challenge for the sustainable development of rare earth permanent magnets. Here, typical (MM,Nd)-Fe-B dual-alloy sintered magnets were prepared to elucidate the effects of misch metal (MM) on magnetization reversal and coercivity. Minor loop measurement, recoil curve analysis, angular-dependent magnetic characterization, and micromagnetic simulation were combined to reveal the reversal behavior and coercivity mechanism. As the MM content increases to around 30 at%, the coercivity decreases from 14.8 kOe to 9.4 kOe, whereas the remanence remains at 13 kGs and the maximum energy product reaches 38.8 MGOe. The coercivity variation with different MM contents is attributed to the asynchronous grain reversal rather than the mechanism transition. Meanwhile, all magnets display obvious temperature-dependent coercivity behavior. Magnetization reversal is nucleation-controlled from 150 to 200 K, pinning- controlled from 250 to 380 K. These findings provide mechanistic guidance for designing low-cost and high-performance permanent magnets using abundant rare earth resources.

ABSTRACT Fluxgate sensors are indispensable for the detection of weak magnetic fields. However, their noise performance remains constrained by an incomplete understanding of the interplay between the high‐frequency magnetization dynamics of the core material and the overall sensor behavior. Unlike conventional quasi‐static evaluation methods, this study identifies the high‐frequency magnetization squareness ratio as a pivotal factor in noise suppression. By implementing optimized isothermal annealing of Co‐based amorphous wires, we achieved precise control over their high‐frequency magnetization characteristics, thereby reducing the sensor noise to 20 pT Hz −1/2 @1 Hz. By using a multi‐scale physical modeling approach, we elucidate the underlying mechanism and establish a clear correlation between microstructural evolution, high‐frequency domain dynamics, and magnetic noise reduction. These findings provide a new framework for material selection and device design in the development of ultra‐low noise fluxgate sensors.

Magnetic random-access memory(MRAM)based on spin-orbit torque(SOT)is a promising non-volatile memory technology for the post-Moore era,owing to its fast switching speed,superior endurance,and potential for low-power operation.However,achieving deterministic current-induced magnetization switching in high-density perpendicular magnetic anisotropy systems,without reliance on external magnetic fields,remains a critical bottleneck,impeding its widespread commercial application.This review surveys recent progress of SOT-driven field-free switching of perpendicular magnetization and gives a coherent overview of symmetry-breaking mechanisms and device-level implications.Strategies that create intrinsic effective fields through engineered structural asymmetry(e.g.,wedged layers and asymmetric interfaces)and built-in gradients such as composition or oxidation profiles are summarized.Approaches based on magnetic interactions,including antiferromagnetic exchange bias and interlayer coupling in multilayer and synthetic antiferromagnetic structures,are also discussed.Then,emerging mechanisms implemented by low-symmetry crystals and topological materials are highlighted,in which nontraditional spin textures and out-of-plane spin polarization contribute to deterministic PMA switching in the absence of external fields.In addition,recent demonstrations of SOT-driven self-switching in magnetic single-layer systems are introduced.Finally,opportunities and remaining challenges for SOT-based spintronic devices are outlined in the context of future information technology,with a focus on determined switching,write-current reduction,thermal stability,device variability,endurance,and CMOS-compatible integration.

High-entropy oxides possess unique structures and physicochemical properties, offering significant application potential across multiple fields. However, their synthesis remains challenging, with one key issue being how to integrate multiple oxide components with different crystal structures into single-phase high-entropy oxide nanoparticles (HEO-NPs). This study developed an oxygen gas-assisted gas-phase non-equilibrium condensation synthesis strategy, successfully preparing hexanary TiVCrFeTaW HEO-NPs comprising five oxide components with different crystal structures. The result shows that the addition of oxygen gas ensures sufficient oxidation of the nanoparticles, effectively inhibiting the formation of core-shell heterostructures caused by incomplete oxidation. The non-equilibrium gas-phase condensation process enables the uniform mixing and formation of a single crystalline phase from the various oxide components with different original structures. The synthesized HEO-NPs have an average particle size of 6-8 nm. Furthermore, by adjusting the sputtering power and gas flow parameters, the structural transition of the high-entropy oxide from amorphous to crystalline states was successfully controlled. This reveals the governing principles of gas flow rate and sputtering power on the crystallinity of the high-entropy oxide: HEO-NPs' crystallinity significantly increases when the gas flow rate is reduced and the sputtering power is increased. This study provides important guidance for the controllable synthesis of high-entropy oxide nanoparticles.

M-type strontium ferrite (SrFe12O19) is widely used in various fields due to its low cost and excellent stability. However, its relatively low saturation magnetization (Ms) significantly restricts its broader applications. Enhancing Ms through non-rare-earth doping via the solid-state reaction method is of significant practical importance. The primary challenge lies in simultaneously maintaining lattice stability and regulating Fe3+ spin alignment through doping. In this study, a series of non-rare-earth Nb-Zn co-doped SrFe12-x(NbaZnb)xO19 (a:b = 1:1, a:b = 4:5, x = 0.1-0.5) were synthesized using the solid-state reaction method. XRD phase analysis indicated that a single M-type strontium ferrite phase was obtained at the stoichiometric doped (a:b = 1:1). In contrast, for the non-stoichiometric doped (a:b = 4:5), a trace amount of the secondary phase SrNb0.5Fe0.5O3 was detected in Nb-Zn doped samples with x >= 0.2. Ms of both stoichiometric and non-stoichiometric doped samples increased within the range of 0 <= x <= 0.3 but gradually decreased when x exceeded 0.3. Notably, for the composition with a: b = 4:5, Ms reached a maximum value of 79.33 emu/g at x = 0.3, accompanied by a synchronous enhancement of 18.5 % in coercivity (Hc). Raman spectroscopy analysis revealed the enhancement mechanism of Ms: the synergistic occupation of Nb5+ and Zn2+ ions. Specifically, Zn2+ preferentially occupies the 4f1 tetrahedral sites, while Nb5+ incorporates into the 4f2 sites. This co-substitution effectively replaces the spin-down Fe3+ ions, leading to a significant increase in Ms. The presence of a trace amount of the secondary phase SrNb0.5Fe0.5O3 in the non-stoichiometrically doped samples, effectively inhibited grain growth, thereby contributing to the enhancement of Hc. This study successfully synthesized non-rare-earth-doped strontium ferrite materials via a solid-state reaction method, achieving a significant enhancement in Ms. Furthermore, the underlying mechanism for the improvement in Ms through Nb-Zn co-doping was elucidated for the first time. Our findings are of significance for the development of high-performance, cost-effective ferrite materials.