The observation of an antisymmetric magnetoresistance in a trilayer van der Waals heterostructure Fe ₃ GeTe ₂ /graphite/Fe ₃ GeTe ₂ .

Finding tunable van der Waals (vdW) ferromagnets that operate at above room temperature is an important research focus in physics and materials science. Most vdW magnets are only intrinsically magnetic far below room temperature and magnetism with square-shaped hysteresis at room temperature has yet to be observed. Here, we report magnetism in a quasi-2D magnet ${\mathrm{Cr}}_{1.2}{\mathrm{Te}}_2$ observed at room temperature (290 K). This magnetism was tuned via a protonic gate with an electron doping concentration up to $3.8\times {10}^{21}{\mathrm{cm}}^{-3}$. We observed nonmonotonic evolutions in both coercivity and anomalous Hall resistivity. Under increased electron doping, the coercivities and anomalous Hall effects (AHEs) vanished, indicating a doping-induced magnetic phase transition. This occurred up to room temperature. DFT calculations showed the formation of an antiferromagnetic (AFM) phase caused by the intercalation of protons which induced significant electron doping in the ${\mathrm{Cr}}_{1.2}{\mathrm{Te}}_2$. The tunability of the magnetic properties and phase in room temperature magnetic vdW ${\mathrm{Cr}}_{1.2}{\mathrm{Te}}_2$ is a significant step towards practical spintronic devices.

The exchange-bias (EB) effect, usually arising in ferromagnetic (FM)-antiferromagnetic (AFM) interfaces with uniaxial magnetic anisotropy, holds high potentials in spintronic applications. Here, we report both field-cooling and zero-field cooling EB effects with a maximal EB field $|H_{EB}|$ reaches up to 3859 Oe in above-room-temperature van der Waals (vdW) ferromagnet ${\mathrm{Fe}}_3\mathrm{Ga}{\mathrm{Te}}_2$ nanoflakes at low temperatures. The observed intrinsic EB effects can be largely tuned via the gate-induced proton intercalation. Moreover, we observe an unusual sign-tunable EB effect under different gate voltages after $\pm 2\mathrm{T}$ field cooling, leading to a crossover between positive and negative EB effects. Theoretical analysis based on density functional theory indicates that the magnetic coupling at the FM/AFM interface in proton-intercalated ${\mathrm{Fe}}_3\mathrm{Ga}{\mathrm{Te}}_2$ is highly controllable and can be tuned to be FMI-1 $(\uparrow /\downarrow \uparrow$, positive EB) or FMI-2 ($\downarrow /\downarrow \uparrow$, negative EB) magnetic configurations, depending on different H-absorption sites. Our experiments offer a knob to control the sign of EB effects and further open opportunities for more applicable spintronic devices in high-temperature vdW ferromagnets.

Layered chiral magnets with broken spatial inversion symmetry (SIS) enable chiral spin textures to occur in atomically thin layers. However, most layered materials retain SIS during their crystallization. Here, we demonstrate that SIS can be broken in a layered transition metal dichalcogenide TaS₂ by intercalating Mn atoms. A chiral magnetic phase in Mn_1/3TaS₂ has, thus, been realized. This phase enables a nonzero Dzyaloshinskii–Moriya interaction, which in turn gives rise to large topological Hall effects (THEs) below 50 K. Both the ferromagnetism and THE can be tuned at low temperatures by modulating the carrier density via a protonic gate. Measured at 20 K with V_g = −4.7 V applied to the gate and electron doping density of 1.7 × 10²² cm⁻³, the maximum THE was almost double that recorded with no gate voltage applied. By further reducing the sample thicknesses, both the Curie temperature T_c and the longitudinal magnetoresistance can be significantly modulated. This is consistent with the theory of critical behavior. Our work highlights the ability to control both magnetism and chiral spin textures in Mn_1/3TaS₂ nanoflakes. Applying this discovery may lead to a variety of practical van der Waals heterostructure devices.

The iron-based superconductor FeSe has garnered considerable attention, in no small part due to its rich physics as well as the unique coexistence of superconductivity and nematicity. The recent discovery of the superconducting diode effect (SDE)—a non-reciprocal critical current with respect to the bias direction—requires simultaneous breaking of time-reversal symmetry (TRS) and inversion symmetry (IS), making it a powerful transport signature of broken symmetries in superconductors. Notably, most reported SDEs rely on the application of an external magnetic field to break TRS, which significantly limits their practical applications in integrated superconducting electronics. Here, we report a field-free SDE in $45°$-twisted FeSe Josephson junctions below $3 \mathrm{K}$, evidenced directly by the even symmetric dependence of the asymmetric critical current on the magnetic field. Under temperature modulation, the SDE is progressively suppressed and ultimately exhibits a polarity reversal at $2.2 \mathrm{K}$. Our findings provide compelling transport evidence for the field-free SDE in iron-based superconductor FeSe, offering a promising platform for exploring symmetry-breaking physics and developing low-dissipation superconducting electronic devices.

The Dzyaloshinskii–Moriya interaction (DMI) is an antisymmetric exchange interaction that favors noncollinear spin configurations and plays an essential role in high-density, low-power magnetic memories. In general, DMI exists in magnetic systems with inversion symmetry breaking and strong spin–orbit coupling. It can also be induced by interface engineering, chemisorption, and so on. However, tailoring DMI by all-electrical means has yet been illustrated so far. In this paper, we report that DMI can be reversibly induced via electrically controlled proton intercalation in van der Waals magnet Cr1.2Te2 nanoflakes, leading to a large topological Hall resistivity up to 0.47 μΩ⋅cm at 3 K. The magneto-ionically coupling induced sizable DMI is further identified by theoretical calculation in the hydrogen intercalated Cr–Te system. In addition, the protonic gated Cr1.2Te2 nanoflakes exhibit large exchange bias effects at low temperatures, suggesting the emergence of antiferromagnetic phase. Our finding establishes that magneto-ionically coupling can not only control the magnetism but also provide an alternative knob to tailor DMI by all-electrical means, allowing for the searching of unconventional magnetic structures in many more two-dimensional (2D) magnets.