ABSTRACT The intrinsic spin‐split band structure and compensated magnetic moments of altermagnets make them promising candidates for spintronic applications. Recently, a magnetic spin Hall effect has been discovered in spin‐split antiferromagnets, including noncollinear antiferromagnets and altermagnets. This effect enables the efficient generation of unconventional spin currents even without spin‐orbit coupling. However, although such nonrelativistic spin currents are proposed to have a magnetic origin, the direct connection between the Néel vector and the spin current polarization is still missing. Here, we report an unconventional spin Hall magnetoresistance (SMR) generated from nonrelativistic spin currents, which exhibits a fundamentally distinct angular‐ and temperature‐dependences compared to conventional SMR. Based on this mechanism, we investigate RuO2, an altermagnetic candidate under debate recently, and unveil its spin current polarization by disentangling the conventional and magnetic spin Hall effects. The results suggest that the nonrelativistic spin current hosts a polarization very close to the Néel vector, unambiguously indicating a magnetic origin. The unconventional SMR not only presents solid evidence helpful to solve the puzzle of state in RuO2, but also paves a straightforward route to harnessing nonrelativistic spin currents in altermagnets for advanced spintronic applications.

Piezotronics, which enables mechanical stimuli to actively shape adaptive and seamless interactions between electronic systems and ambient environments, is becoming increasingly valuable in the Internet of Things, human-machine interfaces, and wearable electronics. Interface-dominated polarization underpins efficient electromechanical transduction in piezotronic sensors; however, it enforces limited performance tunability and hampers multifunctional applications. Here, we use a macroscale tip-induced strain gradient to trigger a bulk-dominated polarization in GaN for realizing a tunable piezotronic effect. Such a mechanism uses interface polar symmetry and shielding of bulk piezo-charges to drive an electrical switching between high- and low-strain sensitivity states. The tunability is preserved across different indenter sizes, while spherical tips with larger radii further enhance the modulation and tuning range due to strain-gradient size effects. Our piezotronic device has a wide sensitivity tunability window of 24 403, a large pressure sensitivity of 223.2 meV·MPa-1, and ultrahigh strain sensitivity of 1.43 × 108. Moreover, the piezotronic device shows exceptional mechanical durability up to 10 000 loading cycles and preserves electrical tunability even under dynamic operation. This study enriches piezotronic physics by uncovering the cooperative roles of bulk polarization and interface symmetry in transport modulation, and establishes a viable strategy for continuous and wide-range performance tunability in a single mechanical sensor.

We demonstrate room-temperature negative differential resistance (NDR) and unsaturated magnetoresistance (MR) effects in germanium-based devices. Our findings indicate that the observed NDR primarily originates from the carrier injection effect induced by local impact ionization in germanium. As the magnetic field increases, the MR values exhibit an unsaturated behavior, increasing quadratically at low fields and transitioning to a linear increase at higher fields, reaching approximately 91% at 1 T. We attribute this large unsaturated MR to carrier inhomogeneity. The equivalent Hall electric field strength was used to characterize the degree of carrier inhomogeneity under magnetic fields: a larger equivalent Hall electric field strength indicates stronger carrier inhomogeneity and consequently a larger corresponding MR. The coexistence of excellent room-temperature NDR and large unsaturated MR in germanium-based devices (achieved by constructing electrodes at two edge positions on the semiconductor surface) enables the development of multifunctional devices.

The fundamental role of magnetic materials in modern science and technology has driven a rapid surge in research on unconventional magnetism in recent years. Among these systems, altermagnets, which simultaneously exhibit zero net magnetization in real space and anisotropic spin splitting in momentum space, have garnered particular interest for both fundamental physics and technological applications. RuO2 stands as the pioneering and most extensively studied candidate in this class. While the intrinsic magnetic order of RuO2 remains a subject of active debate, numerous exotic phenomena characteristic of altermagnetism have been observed experimentally. In this review, we explore various facets of the altermagnetism through specific case studies in RuO2, including its crystal and magnetic structures, electronic band properties, and transport phenomena. We critically assess the debate surrounding the intrinsic magnetism in RuO2, incorporating evidence from altermagnetic signatures in transport with contrasting results from magnetic and spectroscopic measurements. Finally, we discuss possible future research directions on this topic.

Mn5Si3 is a metallic antiferromagnet with rich temperature- and field-driven multiple transitions. Using Cu-flux-grown bulk single crystals, we uncover pronounced anomalies in resistivity and magnetoresistance (MR) below similar to 100 K, indicating successive reconstructions of the antiferromagnetic state. The longitudinal MR shows a strong low-field response with characteristic field scales. Angle-dependent magnetoresistance (ADMR) under in-plane field rotation provides a symmetry-resolved fingerprint: a 2 + 4 + 6 Fourier-series decomposition reveals a clear redistribution of symmetry weights, including a marked enhancement of the sixfold component at low temperature under high field. Reproducible non-sinusoidal features at 20 K and 7 T further suggest rotation-induced rearrangements beyond a static description. These results establish symmetry-sensitive magnetotransport, including ADMR, as an effective probe of complex antiferromagnetic reconstructions in Mn5Si3.

A CMOS-compatible pressure sensor capable of seamlessly bridging external stimuli with modern electronics is essential for advancing applications in wearable systems, human-machine interfaces, and robotics. However, the weak mechanoelectrical coupling of silicon, together with its epitaxial difficulty with piezoelectric semiconductors, has long challenged the development of high-performance Si-based sensors. Here, we report a generalizable mechanical stacking strategy that realizes epitaxial-free, wafer-scale Si/GaN pressure sensors. Both nn and pn junction architectures are constructed to yield electrically tunable pressure response due to the piezotronic effect driven by asymmetrical interfaces and carrier shielding. As a result, the device delivers high pressure sensitivity of 43.34 meV/MPa, exceptional gauge factors of 5.8 × 106, and submillisecond response times. We show that these piezotronic pressure sensors can be used to detect impulsive forces with high temporal resolution, as well as monitor signals of finger rhythms. This work establishes mechanical stacking as a universal integration paradigm for epitaxial-free heterogeneous electronics, enabling high-performance, CMOS-compatible piezotronic sensors.

With the increasing demand for higher storage speed and density in information technology, spin–orbit torque (SOT)-based magnetic random access memory has attracted considerable attention because of its fast read/write operation and high endurance. Rare-earth-transition-metal ferrimagnetic alloys exhibit strong bulk perpendicular magnetic anisotropy and tunable magnetic compensation, which make them promising candidates for high-density and thermally stable SOT devices. In this work, a series of perpendicularly magnetized W/Tb1−xCox/W heterostructure films were fabricated by direct current magnetron co-sputtering. The effects of composition on the magnetic properties, together with the temperature-dependent evolution of the Tb and Co sublattice moments, were systematically investigated. The results reveal a clear composition compensation point at room temperature, where the coercivity shows a pronounced enhancement. Variable-temperature measurements further identify a composition-dependent temperature compensation point (Tcomp), confirming the distinct thermal responses of the two sublattices. In addition, deterministic current-driven magnetization switching was achieved under an in-plane assist field. These findings provide an experiment for optimizing ferrimagnetic SOT devices over a wide temperature range.

Mn 3 Si 2 Te 6 , quasi‐2D ferrimagnetic semiconductor, exhibits anomalous saturated colossal magnetoresistance (CMR) only when a magnetic field is applied along its magnetic hard magnetization axis, suggesting unconventional underlying physics and promising potential for spintronic applications. However, the intrinsic mechanism behind this anomalous anisotropic CMR remain unresolved. In this work, the temperature and angular dependencies of magnetoresistance (MR) in high‐quality Mn 3 Si 2 Te 6 single crystals are systematically investigated. The MR measured within the easy ab ‐plane shows no saturation, whereas a large negative saturation MR of ≈ −100% is observed along the hard magnetization c ‐axis below the Curie temperature. To explain this behavior, a novel model is proposed in which in‐plane magnetic fields induce quasi‐2D magnetotransport, while out‐of‐plane fields promote a transition to 3D transport. Notably, when the c ‐axis field exceeds the demagnetizing field, the alignment between spin‐polarized carriers and magnetic moments significantly suppresses scattering. The results challenge the applicability of the chiral orbital currents (COC) model in Mn 3 Si 2 Te 6 single crystals and establish a new framework for controlling the CMR effect in layered magnets, offering a pathway toward future spintronic technologies.

Mn3Si2Te6, quasi-2D ferrimagnetic semiconductor, exhibits anomalous saturated colossal magnetoresistance (CMR) only when a magnetic field is applied along its magnetic hard magnetization axis, suggesting unconventional underlying physics and promising potential for spintronic applications. However, the intrinsic mechanism behind this anomalous anisotropic CMR remain unresolved. In this work, the temperature and angular dependencies of magnetoresistance (MR) in high-quality Mn3Si2Te6 single crystals are systematically investigated. The MR measured within the easy ab-plane shows no saturation, whereas a large negative saturation MR of ≈ -100% is observed along the hard magnetization c-axis below the Curie temperature. To explain this behavior, a novel model is proposed in which in-plane magnetic fields induce quasi-2D magnetotransport, while out-of-plane fields promote a transition to 3D transport. Notably, when the c-axis field exceeds the demagnetizing field, the alignment between spin-polarized carriers and magnetic moments significantly suppresses scattering. The results challenge the applicability of the chiral orbital currents (COC) model in Mn3Si2Te6 single crystals and establish a new framework for controlling the CMR effect in layered magnets, offering a pathway toward future spintronic technologies.

In order to evaluate the anti-magnetic-field interference ability of silicon-based electronic components, this work takes two types of commercial silicon-based diodes, i.e., the p-n diode (1N4148 model as an example) and Schottky diode (DSK26 model as an example), as the main research objects. Firstly, we systematically study the evolution of the current-voltage characteristics of the two types of silicon-based diodes under 1 T external magnetic fields at room temperature. Based on the fitting results of Schottky transport theory and the analysis of magnetoresistance effect theory, we have determined that the ideality factors, reverse saturation current density, and resistance of these two types of diodes exhibit significantly different evolution patterns with the applied magnetic field. The corresponding performance parameters of these two diodes are compared and discussed. In addition, we studied the resistance evolution of the 1N4148 p-n diode under the 32 T pulsed high magnetic field. We found that the resistance of the bipolar-driven device increases with the increase of the magnetic field strength. The resistance of the p-n diode increases from about 630 Ω @ 1 mA and 77 Ω @ 10 mA under zero magnetic field to 740 Ω @ 1 mA and 95 Ω @ 10 mA under 32 T, respectively. This indicates that the high magnetic field has limited emphasis on the ratio of electron concentration to hole concentration in the space charge region of the intrinsic bipolar transport device. The results of this work will provide an important reference for the resistance of semiconductor silicon-based electronic components to external magnetic field interference.

In this work, we report the experimentally observed nonlinear dependence of Hall resistance on current in a Pt/RuO _2 bilayer structures. Temperature-dependent measurements reveal that the Hall resistance is highly sensitive to temperature variations. The first-principles calculations suggest that the nonlinear dependence of Hall resistance on current may arise from changes in the Berry curvature induced by the electric field. Based on Pt/RuO _2 (101) films, we developed a temperature sensor with a wide range, high precision, and excellent reliability. This work provides strategies for temperature sensing and promotes the future application of Hall temperature sensors.

Nonmagnetic-metal/ferromagnetic heterostructures have drawn extensive attention due to the generation of spin–orbit torque (SOT). This work is based on the large spin Hall angle observed in Pt0.70(GdOy)0.30 composite films, we focus on investigating the sharp sign reversal of the damping-like SOT induced by antiferromagnetic coupling at the NiFe/Pt1−x(GdOy)x (x ≥ 0.30) interface. Such interface-modulated SOT is found to be suppressed by inserting an ultra-thin copper spacer layer using spin-torque ferromagnetic resonance. Meanwhile, the relevant interfacial parameters further indicate the key importance of interfacial magnetic coupling for boosting spin transport efficiency. The superconducting quantum interference device tests on NiFe/Pt1−x(GdOy)x (x ≥ 0.30) structures reveal that the magnetization in Pt1−x(GdOy)x is antiparallel to that of NiFe, forming an antiferromagnetically coupled configuration at the NiFe/Pt1−x(GdOy)x interface. Our results highlight the promising application of rare earth materials in spin transport, and the construction of interfacial antiferromagnetic coupling opens a route to modulate SOT.

The fundamental role of magnetic materials in modern science and technology has driven a rapid surge in research on unconventional magnetism in recent years. In particular, altermagnets, which simultaneously exhibit zero net magnetization in real space and anisotropic spin splitting in momentum space, have garnered significant interest for both fundamental physics and technological applications. Among these, RuO_2 stands as the pioneering and most extensively studied altermagnet. While the intrinsic magnetic order of RuO_2 is still a subject of active debate, numerous exotic phenomena characteristic of altermagnetism have been observed in RuO_2 samples. In this review, we explore each facet of the altermagnetism through specific case studies in RuO_2, systematically surveying its crystal and magnetic structures, electronic band properties, and transport phenomena. We critically assess the debate surrounding the intrinsic magnetism in RuO_2, incorporating evidence from altermagnetic signatures in transport, as well as contrasting results from magnetic and spectroscopic measurements. Finally, possible future research directions in this field are discussed.

(RuO 2 , a prototypical altermagnetic material, has attracted considerable interest in recent years. However, there is still experimental controversy over the antiferromagnetic order of RuO 2 , and little is known about its Néel vector orientation and its dynamic behavior in an external magnetic field. Here, based on the experimental results of magnetoresistance (MR) and anisotropic MR properties of RuO 2 films, the theoretical analysis reveals that the Néel vector deviates from the [001] direction, instead rotating within the (−110) plane at an angle of 26.1° with respect to the z ‐axis of the RuO 2 . Meanwhile, the magnetic moment of Ru atoms is slightly perturbed around the direction of the Néel vector at 9 T, with a maximum perturbation angle along (−110) in‐plane and out‐of‐plane directions of ≈0.47°±0.02° and 0.57°±0.05°, respectively. The anisotropic exchange stiffness constants of the RuO 2 film are calculated for the first time. Furthermore, through spin Hall MR measurements in RuO 2 (110)/Pt bilayer, clear Néel‐vector‐related saturation‐like behavior and sharp angular transitions are observed. The interfacial spin‐mixing conductance at the RuO 2 (110)/Pt bilayers is estimated to be 2.41 × 10 16 m −2 . This study provides experimental evidence for the magnetic ordering in RuO 2 films and elucidates the dynamics of its Néel vector under high magnetic fields).

The anomalous Hall effect and spin–orbit torque of TbCo-based multilayer films have been methodically studied in recent years. Many properties of the films can be obtained by the anomalous Hall resistance loops of the samples. We report on the effects of a structure composed of two heavy metals as the buffer layers on the anomalous Hall resistance loops of TbCo-based multilayers at different temperatures. The results showed that the coercivity increases dramatically with decreasing temperature, and the samples without perpendicular magnetic anisotropy at room temperature showed perpendicular magnetic anisotropy at low temperatures. We quantified the spin–orbit torque efficiency and Dzyaloshinskii–Moriya interaction effective field size of the films W/Pt/TbCo/Pt at room temperature by measuring the loop shift of anomalous Hall resistance. The results showed that the study of anomalous Hall resistance loops plays an important role in the study of spintronics, which can not only show the basic properties of the sample, but can also obtain other information about the sample through the shift of the loops.

Non-magnetic semiconductor materials and their devices have attracted wide attention since they are usually prone to exhibit large positive magnetoresistance（MR） effect in a low static magnetic field environment at room temperature.However, how to obtain a large room-temperature negative MR effect in them remains to be studied. In this paper, by designing an Au/n-Ge:Sb/Au device with metal electrodes located on identical side, we observe an obvious room-temperature negative MR effect in a specific 50 T pulsed high magnetic field direction environment, but not in a static low magnetic field environment. Through the analysis of the experimental measurement of the Hall effect results and bipolar transport theory,we propose that this unconventional negative MR effect is mainly related to the charge accumulation on the surface of the device under the modulation of the stronger Lorentz force provided by the pulsed high magnetic field. This theoretical analytical model is further confirmed by regulating the geometry size of the device. Our work sheds light on the development of novel magnetic sensing, magnetic logic and other devices based on non-magnetic semiconductors operating in pulsed high magnetic field environment.

It is of great importance to search for materials with giant spontaneous exchange bias effect (SEB) at room temperature, as it has wide application prospects in information storage technology, etc. In this work, we observe a giant SEB in antiferromagnetic Fe3BO6 polycrystals, the value of the spontaneous exchange bias field at room temperature is as large as about 4234 Oe. The room-temperature training effect as well as the temperature and the maximum measured field dependence of the [[EQUATION]] are investigated, respectively. We propose that this giant SEB originates from the exchange-coupling interactions between the surface weak ferromagnet state and the bulk antiferromagnet state. The results of this investigation will help to find promising candidate materials for a device based on the SEB effect.

Ni44.1Fe33.2Ga22.8 (NFG) Heusler alloy nanowires were fabricated using a pulsed electrodeposition method. The challenge of co-depositing the Ga element in ternary alloy nanowires was addressed by employing dual complexing agents, high current, and high Ga ion concentrations. The nanowire structure was confirmed to be the B2 phase through XRD and TEM analyses. Furthermore, elemental mapping and multiple-point EDS measurements verified the homogeneous composition distribution within the nanowires. The nanowires exhibited diameters of approximately 70 nm and lengths ranging from 3 to 5 μm. The magnetic properties, including M-H and M-T dependencies, Landé g-factor, and saturation magnetization (Ms), were characterized using a vibrating sample magnetometer (VSM) and ferromagnetic resonance (FMR) techniques. No martensitic transformation was observed in the nanowires within the temperature range of 80 to 370 K. Ultimately, this work provides a fabrication strategy for the co-deposition of elements with significant potential differences in multi-component alloy electrodeposition systems.

The perpendicular magnetic anisotropy (PMA) and spin-orbit torque (SOT) of the TbCo based multilayer films have been methodically studied in recent years. Especially in improving the efficiency of SOT, PMA is a prerequisite for achieving high efficiency. We report on the effects of W/Pt and Pt as the buffer layers on the PMA of TbCo based multilayers at different temperature. The results showed that the coercivity increases dramatically with decreasing temperature, and the samples without PMA at room temperature showed PMA at low temperatures. At room temperature, the structure composed of two heavy metals as buffer layer has more stable and superior performance than the structure composed of one heavy metal as buffer layer. We quantified the spin-orbit torque efficiency and Dzyaloshinskii-Moriya interaction (DMI) effective field size of the films W/Pt/TbCo/Pt at room temperature through our own experimental test platform. Our research not only promotes the study of measurement methods, but also extends the study of spin-orbit torque induced by interface effects of heavy metals.

Spin current plays a central role in spintronics for driving exotic spin-dependent phenomena and high-performance device applications. Recently, a magnetic spin Hall effect has been discovered in spin-split antiferromagnets including noncollinear antiferromagnets and altermagnets, allowing the efficient generation of unconventional spin currents even in the absence of spin-orbit coupling. However, although such nonrelativistic spin currents are proposed to have a magnetic origin, the direct connection between the Neel vector and the spin current polarization is still missing. Here, using the altermagnetic RuO2 as a representative example, we unveil the spin current polarization by disentangling the conventional and magnetic spin Hall effects using a technique we developed based on the spin Hall magnetoresistance measurement. The results suggest that the nonrelativistic spin current hosts a polarization very close to the Neel vector. Our work offers unambiguous evidence of the magnetic origin of the nonrelativistic spin current in altermagnetic RuO2, and paves a straightforward route to understand the unconventional spin currents that are crucial in spintronics.