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

Magnetic frustrated materials are of great interest for their novel spin-dependent transport properties. We report an anisotropic anomalous Hall effect in the triangular itinerant ferromagnet ${\mathrm{Fe}}_3{\mathrm{GeTe}}_2$. When the current flows along the $ab$ plane, ${\mathrm{Fe}}_3{\mathrm{GeTe}}_2$ exhibits the conventional anomalous Hall effect below the Curie temperature $T_c$, which can be depicted by Karplus–Luttinger theory. On the other hand, the topological Hall effect shows up below $T_c$ with current along the $c$ axis. The enhancement of Hall resistivity can be attributed to the chiral effect during the spin-flop process.

The weak interlayer coupling in van der Waals (vdW) magnets has confined their application to two dimensional (2D) spintronic devices. Here, we demonstrate that the interlayer coupling in a vdW magnet ${\mathrm{Fe}}_3{\mathrm{GeTe}}_2$ (FGT) can be largely modulated by a protonic gate. With the increase of the protons intercalated among vdW layers, interlayer magnetic coupling increases. Because of the existence of antiferromagnetic layers in FGT nanoflakes, the increasing interlayer magnetic coupling induces exchange bias in protonated FGT nanoflakes. Most strikingly, a rarely seen zero-field cooled (ZFC) exchange bias with very large values (maximally up to 1.2 kOe) has been observed when higher positive voltages ($V_g\ge 4.36\mathrm{V}$) are applied to the protonic gate, which clearly demonstrates that a strong interlayer coupling is realized by proton intercalation. Such strong interlayer coupling will enable a wider range of applications for vdW magnets.

Nontrivial spin configurations tend to bring about novel transport properties in magnetic materials. We report the magnetic anisotropy and topological Hall effect in trigonal ${\mathrm{Cr}}_5{\mathrm{Te}}_8$ single crystals. Below the magnetic transition temperature, the spins are canted ferromagnetic aligned along $c$ axis with antiferromagnetic components in $ab$ plane. This peculiar magnetic structure gives rise to the anisotropic anomalous Hall effect (AHE) in ${\mathrm{Cr}}_5{\mathrm{Te}}_8$. When the current flows along the $ab$ plane, ${\mathrm{Cr}}_5{\mathrm{Te}}_8$ exhibits a conventional AHE depicted by skew scattering mechanism. On the other hand, the topological Hall effect appears with current along $c$ axis, which stems from the noncoplanar spin configuration with scalar spin chirality during the spin flop process.

We study the spin reorientation in ${\mathrm{Fe}}_3{\mathrm{Sn}}_2$ by examining the anisotropic magnetoresistivity in detail, exploiting the dependence of the resistivity on the direction between magnetization and applied current. We determine the distribution of the magnetic domains as a function of temperature between 360 K and 2 K and find the reorientation transition to peak at 120 K. We discover that both out-of-plane and in-plane phases coexist at temperatures around the spin reorientation, indicative of a first-order phase transition. Although the volume of the magnetic domains in the different phases sharply changes at the spin reorientation transition, no appreciable changes in the electronic structure for a specific magnetization is detected by anisotropic magnetoresistivity at the spin reorientation. In contrast, we observe an electronic transition around 40 K, hitherto unreported, and reflected in both the zero-field resistivity and anisotropic resistivity.

While the monolayer sheet is well-established as a Mott-insulator with a finite energy gap, the insulating nature of bulk 1T-TaS₂ crystals remains ambiguous due to their varying dimensionalities and alterable interlayer coupling. In this study, we present a unique approach to unlock the intertwined two-dimensional Mott-insulator and three-dimensional band-insulator states in bulk 1T-TaS₂ crystals by structuring a laddering stack along the out-of-plane direction. Through modulating the interlayer coupling, the insulating nature can be switched between band-insulator and Mott-insulator mechanisms. Our findings demonstrate the duality of insulating nature in 1T-TaS₂ crystals. By manipulating the translational degree of freedom in layered crystals, our discovery presents a promising strategy for exploring fascinating physics, independent of their dimensionality, thereby offering a “three-dimensional” control for the era of slidetronics.