Abstract Magnetic tunnel junctions, as promising emerging spintronic devices, exhibit versatile capabilities in microwave detection and energy harvesting. Here, we modulate the rectification behavior of perpendicular magnetic anisotropy (PMA) based magnetic tunnel junction devices through adjusting the orientation of the external magnetic field, which allows the microwave detection performance to switch from a single-frequency response to a broadband one. The frequency bandwidth can reach up to 1.7 GHz and the maximum sensitivity can attain 270 mV/mW without a bias current. According to experimental analysis, this phenomenon originates from the different behavior of the free layer magnetic moment induced by the magnetic field. The frequency bandwidth dependence is qualitatively explicated by Landau-Lifshitz-Gilbert (LLG) equation. This key advancement effectively broadens the application prospects of magnetic tunnel junction-based microwave detectors.

Surface alignment of a recently discovered ferroelectric nematic liquid crystal (NF) is usually achieved using buffed polymer films, which produce a unidirectional polar alignment of the spontaneous electric polarization. We demonstrate that photosensitive polymer substrates could provide a broader variety of alignment modes. Namely, a polyvinyl cinnamate polymer film irradiated by linearly polarized ultraviolet (UV) light yields two modes of surface orientation of the NF polarization: (1) a planar apolar mode, in which the equilibrium NF polarization aligns perpendicularly to the polarization of normally impinging UV light; the NF polarization adopts either of the two antiparallel states; (2) a planar polar mode, produced by an additional irradiation with obliquely impinging UV light; in this mode, there is only one stable azimuthal direction of polarization in the plane of the substrate. The two modes differ in their response to an electric field. In the planar apolar mode, the polarization can be switched back and forth between two states of equal surface energy. In the planar polar mode, the field-perturbed polarization relaxes back to the single photoinduced "easy axis" once the field is switched off. The versatility of modes and absence of mechanical contact make the photoalignment of NF attractive for practical applications.

Using first-principles calculations, we explore the electronic and topological properties of Janus VAZ3H single layers (A = Si, Ge; Z = N, P) that are dynamically and thermally stable. In the strain-free state, VSiN3H, VSiP3H, and VGeN3H demonstrate direct bandgap ferrovalley (FV) semiconducting properties, while VGeP3H displays an indirect bandgap. The easy magnetization axis varies among these materials, with VSiN3H and VGeN3H preferring in-plane magnetization, whereas VSiP3H and VGeP3H favor out-of-plane magnetization. Furthermore, the electronic structure analysis reveals valley polarization at the K and K' points. When subjected to strain, these systems experience phase transitions, such as direct-to-indirect bandgap shift, the evolution from FV semiconducting to half-valley metal (HVM), and the emergence of a quantum anomalous Hall (QAH) phase within certain strain intervals. The QAH phase is identified by chiral edge states and quantized anomalous Hall conductivity (AHC), supported by an integer AHC plateau of 1e2/h and a Chern number of 1. These results highlight the tunability of VAZ3H SLs through strain engineering, providing a potential platform for valleytronic and topological applications.

With the rise and wide applications of 3D heterogeneous integration technology, inductive voltage regulators have become increasingly important for mobile terminals and high-computing-power devices, while also offering significant development opportunities for high-frequency soft magnetic films. Based on the requirements of onchip power inductors, we first review the advantages and limitations of three types of magnetic core films: permalloy, ·Co-based amorphous metallic films, and FeCo-based nanogranular composite films, with a focus on the technical requirements and challenges posed by several μm-thick laminated magnetic core films. Secondly, almost all on-chip inductors are hard-axis excited, meaning that the field of inductors should be parallel to the hard axis of the magnetic core. We thus compare the characteristics of two types of large-area film fabrication methods, i.e. applying in-situ magnetic field and oblique sputtering, both of which can effectively induce in-plane uniaxially magnetic anisotropy (IPUMA). Their impacts on the static and high-frequency soft magnetic properties are also compared. The influence of film patterning on the domain structures and highfrequency magnetic losses of magnetic cores, as well as corresponding countermeasures, are also briefly analyzed. Furthermore, the temperature stability of magnetic permeability and anisotropy of magnetic core films is discussed from the perspectives of process compatibility and long-term reliability. Although the Curie temperature and crystallization temperature of the three types of magnetic core films are relatively high, the upper limits of their actual process temperatures are affected by the thermal effects on the alignment of magnetic atomic pairs, microstructural defects, and grain size. Finally, the current bottlenecks in testing high-frequency and large-signal magnetic losses of magnetic core films are addressed, and potential technical approaches for achieving magnetic core films that meet the future demands of on-chip power inductors for higher saturation current and lower magnetic losses are outlined.

First-principles calculations within the spin polarized density functional theory (SP-DFT) were used to study the stability, electronic and magnetic properties of a vdW heterostructure by stacking a MXene (Ca 2...

Half-metallic ferromagnetism with tunable magnetic anisotropy in Fe-doped MoTe2 monolayer: A first-principles study

Lanthanide single-molecule magnets (SMMs) continue to draw attention as potential building blocks for ultra-dense data storage devices due to their bistable magnetic ground states and pronounced magnetic anisotropy. To realise this potential, however, a deeper understanding of how molecular magnetic memory responds to structural and environmental perturbations is critical. One essential criterion is the retention of magnetic bistability in the presence of nearby charge or charge fluctuations. Air-stable Dy(iii) SMMs with pseudo-D 5h symmetry are known to exhibit extremely slow magnetic relaxation, attributed to a strong axial crystal field and symmetry-imposed suppression of quantum tunnelling of magnetisation (QTM). Here we report a new high-performance, hybrid compound, [Dy(H2O)5(Cy3PO)2][Mo12PO40]·2(Cy3PO)·4THF·2H2O·Et2O (1), incorporating the bulky polyoxometalate [Mo12PO40]3- in the second coordination sphere. Upon exposure to UV light or X-rays, partial reduction of Mo(vi) to Mo(v) (ca. 3%) yields 1Red, a hybrid material that demonstrates enhanced magnetic blocking, evidenced by increased T B(Hyst) and T IRREV relative to 1. Importantly, we introduce a dilution strategy using an optically dilute, diamagnetic KBr matrix to enhance Mo reduction. This approach boosts Mo(v) content to ca. 30% in 1Red@KBr while preserving the slow relaxation dynamics of the Dy(iii) complex. These results highlight the magnetic resilience of the [Dy(H2O)5(Cy3PO)2]3+ motif in charged environments and establish a basis for exploring magneto-optical and magneto-electric behaviours in SMM hybrid materials.

The first air-stable sandwich complexes TPPLnCp* (Ln = Y, Tb, Dy, Ho, and Er) containing tetraphenylporphyrinate and pentamethylcyclopentadienide ligands were synthesized. Tb 3+ , Dy 3+ , and Er 3+ derivatives are field-induced single-molecule magnets.

Abstract We report experimental evaluation of the thermal stability factor, ∆, for MRAM bits with perpendicular magnetic anisotropy and magnetic free layer diameter of about 20 nm, using magnetic field and spin transfer torque (STT) excitations to accelerate switching and we compare the results to the value obtained by thermal-only excitation. We find that fitting the magnetic switching field distributions to a macrospin model results in identical values of ∆ mean and sigma as determined by direct thermal excitation, also known as retention bake method. On the other hand, fitting the pulse width dependence of the STT switching voltages in the thermal activation regime can either underestimate or overestimate ∆ depending on the choice of the exponent ξ that defines scaling of ∆ with STT. We find the best agreement for ξ = 1.45.

Abstract In this work, a voltage-gated scheme for controlling the transport of skyrmions in nanoracetracks is proposed by using micromagnetic simulations. The scheme utilizes strain-mediated voltage control of magnetism to effectively modulate local magnetic parameters, including perpendicular magnetic anisotropy, exchange stiffness, the Dzyaloshinskii-Moriya interaction, and saturation magnetization. To understand the effect of voltage-controlled magnetism on skyrmion transport, the dynamic behavior of skyrmions was investigated by varying local magnetic parameters at different driven current densities, thereby revealing the physical mechanism. The results demonstrate that skyrmion annihilation, trapping, blocking, and unblocking can be effectively controlled by coordinating the driving current with the local magnetic parameters. Our scheme offers a practical, low-power electrical control strategy for designing spintronic devices based on skyrmion dynamics.

Abstract Enhancing spin-to-charge (S→C) conversion efficiency remains a key challenge in spintronic materials research. In this work we investigate the effect of substrate-induced strains onto the S→C efficiency. On one hand, we analyze strains-induced magnetic anisotropies in yttrium iron garnet (Y 3 Fe 5 O 12 , YIG) by comparing the magnetic and structural properties of YIG films grown on Gd 3 Ga 5 O 12 (GGG) and (CaGd) 3 (MgZrGa) 5 O 12 (SGGG) substrates. Differences in lattice mismatch -YIG//GGG (η = -0.06 %) and YIG//SGGG (η = -0.83 %) -lead to out-of-plane tensile strains in the first case and unexpected compressive strain in the latter. On the other hand, we study the spin injection efficiency on Pt/YIG bilayers evaluated by the Inverse Spin Hall Effect (ISHE). We find that the resulting perpendicular magnetic anisotropy in YIG//SGGG, while not dominant over shape anisotropy, correlates with enhanced ISHE signals as observed in Spin Pumping Ferromagnetic Resonance (SP-FMR) and Spin Seebeck effect (SSE) experiments. Strain engineering proves effective in enhancing spin-to-charge conversion, providing insight into the design of efficient spintronic devices.

ABSTRACT The stability of intelligent life and industry primarily relies on the signal interference shielding among different equipment. The key challenge lies in efficient absorption of electromagnetic waves within the C‐band, which dominates the satellite internet, high‐speed WLAN, and 5/6G communication spectra. Herein, the structural symmetry and surface anisotropy co‐dominated magnetic engineering has been proposed to realize the effective electromagnetic wave absorption within 4–8 GHz. The hierarchical structural morphology optimization has been first developed to guide the configuration integration of symmetric anisotropy, streamline surface, and porous for CoNi‐based alloys. Such hierarchical architecture allows synergy of diversified magnetic configuration, external domain symmetry, and enhanced dipolar coupling interaction, dramatically enhancing magnetic resonance absorption within C‐bands. Our results provide a preparation idea for acquiring precise modulation of magnetic resonance eigenfrequency while realizing high‐performance low‐frequency microwave absorbers.

Ultrafast magnetization switching is essential for spintronic applications, yet the switching speed of current-driven approaches such as spin-transfer torque and spin–orbit torque is fundamentally limited by magnetic damping. Here, we demonstrate voltage-driven switching in perpendicular magnetic tunnel junctions with an exchange-coupled free layer, combining voltage-controlled magnetic anisotropy and voltage-controlled exchange coupling. We achieve unidirectional reversal with a 50% probability within 87.5 ps, establishing the sub-100-ps capability of voltage-induced switching. Analysis of switching probability vs pulse width reveals an intrinsic size-dependent switching efficiency, which is enhanced as device dimensions decrease. This trend reflects the role of coupling dynamics as confirmed by macrospin simulations, establishing coupling dynamics as the key enabler of ultrafast voltage-driven switching.

Magneto-photoluminescent hybrid materials (MPHMs) were prepared by incorporating cobalt ferrite nanoparticles (CFNs) into the fluorescent polymer poly(terephthalaldehyde-undecan-2-one) (PT2U). The CFNs, with a mean size of 3.95 nm, formed aggregates within the PT2U matrix (650–1042 nm) due to surface and interfacial interactions, modulating aggregate morphology and interparticle coupling. Magnetization studies revealed non-monotonic variations in saturation magnetization (30.3–16.2 emu/g), mean blocking temperature (39.3–43.1 K) and effective magnetic anisotropy energy density (2.14 × 106–1.31 × 106 erg/cm3) with increasing CFN content, consistent with the presence of canted surface spins and enhanced magnetizing interparticle interactions. Photoluminescence exhibited progressive quenching, dominated by collisional mechanisms at low CFN content and by interfacial CFN–PT2U interactions at higher loadings. Under a magnetic field (800 Oe), additional quenching occurred, attributed to magnetically induced polymer-chain rearrangements that disrupted the molecular stacking required for efficient aggregation-induced emission. These results demonstrate tunable magneto-photoluminescent coupling in MPHMs governed by surface and interfacial phenomena, providing insights for the design of functional and responsive hybrid materials.

2D Van der Waals ferromagnet Fe5-xGeTe2 (F5GT) is promising for spintronic applications due to its high Curie temperature, layered structure, and ability to host complex magnetic textures. However, the origin of its sample-dependent magnetic anisotropy remains unclear, hindering control of its magnetic behavior. Here, spatially resolved cryogenic scanning transmission electron microscopy (STEM) is used to correlatively map magnetism, lattice structure, and chemistry across atomic-to-micron scales. This is revealed that only mesoscale, not nanoscale, inclusions of a Fe-deficient secondary phase significantly modify magnetic behavior, establishing a previously unrecognized critical length scale. This phase separation, induced by quenching, leads to in-plane magnetic anisotropy, while slow cooling confines separation to a few nanometers and preserves out-of-plane anisotropy. These findings reconcile prior inconsistencies and establish a predictive framework for tuning magnetism in F5GT through thermal processing, with broader implications for controlling anisotropy in other 2D magnetic materials.

Magnetic Relaxometry (MRX) is a promising technique for probing the magnetic properties of nanoparticles with considerable potential in biomedical applications. It magnetizes magnetic nanoparticles through a direct current magnetic field to obtain measurable Néel relaxation signals when magnetic nanoparticles are combined with specific cells or antibodies. It employs highly sensitive magnetic sensors to record relaxation signals following nanoparticle magnetization, from which intrinsic parameters and quantitative information can be extracted, and ultimately completes mass detection. The essential step in MRX-based mass detection is to establish the calibration relationship between the relaxation signal amplitude reflecting the magnetic moment and the corresponding mass of magnetic nanoparticles. In this article, we present a parameter estimation and quantification framework that integrates an improved Particle Swarm Optimization (PSO) algorithm with the Moment Superposition Model (MSM) as the objective function. The proposed method effectively combines experimental data with a theoretical model, enabling accurate determination of key intrinsic parameters, including saturation magnetization and magnetic anisotropy. Building on these reliable estimating parameters, the proposed PSO algorithm is further applied to quantify nanoparticle mass. Validation through simulations and experimental data confirms the robustness of the method, with the final mass detection error reaching the microgram level. These results highlight its potential for precise characterization of magnetic nanoparticles in biomedical contexts.

The precise detection of a perpendicular Néel vector in collinear antiferromagnetic (AFM) materials has long been expected for advancing two-dimensional AFM spintronics. Here, we proposed the perpendicular Néel vector detection using the layer Hall effect in collinear antiferromagnets down to the monolayer limit. Through materials screening, the Co2S2 is identified as a prototypical AFM monolayer with the spin-layer coupling and perpendicular magnetic anisotropy. Thanks to the electrically engineered layer-locked band edges and Berry curvatures from spin-layer coupling, a sizable layer-polarized anomalous Hall conductivity of σxy up to ∼110 S/cm is obtained in monolayer Co2S2. Intriguingly, the sign of σxy changes when the Néel vector is reversed, providing an efficient route for detecting the AFM order. Moreover, the achievement of the Néel vector detection via the layer Hall effect is further demonstrated in altermagnetic monolayer Ca(CoN)2. The present findings open an avenue to explore the Néel vector detection for atomic-scale AFM materials and spintronic devices.

Abstract Turbulence is a ubiquitous process that transfers energy across many spatial and temporal scales, thereby influencing particle transport and heating. Recent progress has improved our understanding of the anisotropy of turbulence with respect to the mean magnetic field; however, its exact form and implications for magnetic topology and energy transfer remain unclear. In this study, we investigate the nature of magnetic anisotropy in compressible magnetohydrodynamic turbulence within low- β solar wind using measurements from the Cluster spacecraft. By decomposing small-amplitude fluctuations into Alfvén and compressible modes, we reveal that magnetic anisotropy is largely mode dependent: Alfvénic fluctuations are broadly distributed in propagation angle, whereas compressible fluctuations are concentrated near the quasi-parallel (slab) direction, a feature closely linked to collisionless damping of compressible modes. For β → 0, compressible modes become dominant within the slab component at smaller scales. These findings advance our understanding of magnetic anisotropy in solar wind turbulence and offer a new perspective on the three-dimensional turbulence cascade, with broad implications for particle transport, acceleration, and magnetic reconnection.

Lanthanide complexes with a low-symmetry ligand environment are frequently observed to exhibit good single molecule magnet (SMM) behavior, which is seemingly at odds with the established understanding that strong Ising-type magnetic anisotropy is essential. This and other paradoxical features of such clusters are shown to follow naturally from a semiclassical treatment of the ligand field, which becomes valid in the limit of large total angular momentum J. Quantum corrections are discussed qualitatively. The resulting physical picture offers clear insight into a broad class of lanthanide-based SMMs.

High magnetic anisotropy materials have critical applications in numerous technology sectors, largely relying on rare-earth and precious metals which poses major sustainability challenges. The high entropy composition space offers a vast arena for exploration of high magnetic anisotropy materials based on earth-abundant elements. However, common high entropy alloys favor disordered cubic crystal structures whereas ordered uniaxial structures are necessary for the desirable strong magnetic anisotropy. Here we report the discovery of novel quinary borides with C16 uniaxial crystal structure and high magnetic anisotropy. Switching the easy-plane anisotropy of binary C16 borides to easy-axis can be achieved through a suitable mixing of Fe and Co on the transition metal sublattice. Using a combinatorial sputtering approach, we explore the wider high entropy composition space to further enhance the anisotropy of the C16 phase by incorporation of additional magnetic 3d transition metals. Significant coercivity increase, more than two-fold, has been observed, compared with binary and ternary transition metal borides. Density functional theory calculations support the experimental findings, predicting anisotropy approaching 107erg/cm3, which is understood in terms of the optimized electronic structure of the high entropy borides. These results establish a promising boron-assisted synthesis strategy to achieve strong magnetic anisotropy using earth-abundant elements.