We explore the large magnetoresistance (MR) in hBN/few-layer-graphene/CrSBr/few-layer-graphene heterostructures and reveal the mechanism behind its non-monotonic bias dependence. Using bias voltage and temperature as independent tuning knobs, we achieve MR up to 350 at 20K, characterized by symmetric M-shaped maxima around ± 0.5 V. Continuous tuning of the magnetization angle θ via a hard-axis magnetic field shows that the barrier band-edge offset varies linearly with cos(θ/2), a first-order signature of spin-dependent interlayer hybridization. This linear relationship rules out the Jullière model and a spin-filter projection. We conclude that the magnetic-configuration-dependent band edge, rather than electrode spin polarization, dictates the large magnetoresistance in CrSBr junctions.

van der Waals (vdW) heterostructures are a groundbreaking platform for modern spintronics, offering atomically precise interfaces that enable unprecedented control over material properties. This perspective explores exchange bias (EB), a cornerstone of spintronic functionality arising from interfacial coupling between ferromagnetic (FM) and antiferromagnetic (AFM) layers, in such systems. Unlike conventional thin-film heterostructures, vdW materials, which exhibit weak interlayer coupling, tunable vdW gaps, and layer-dependent magnetism, challenge classical models of EB and open new research directions. We review EB phenomena in vdW heterostructures, highlighting key observations that deviate from conventional thin-film models and outlining the underlying structural and magnetic intricacies of these systems. We highlight how these phenomena lead to an unconventional EB thickness dependence and self-induced EB without a separate AFM layer. We also explore the role of interface imperfections that can arise from the reactive nature of vdW materials and their impact on EB. Finally, we discuss mechanisms to control EB and outline the potential of leveraging robust EB in these materials for future memory devices.

Van der Waals (vdW) magnetic heterostructures offer a versatile platform for engineering interfacial spin interactions with atomic precision, enabling nontrivial spin textures and dynamics behavior. In this work, robust asymmetric magnetization reversal and exchange bias are reported in Fe3GeTe2 (FGT), driven by interlayer exchange coupling with the A-type antiferromagnet CrSBr. Despite the orthogonal magnetic anisotropies-out-of-plane easy axis in FGT and in-plane in CrSBr-a strong interfacial exchange interaction that gives rise to pronounced and switchable exchange bias and asymmetric switching in FGT is observed, persisting up to the Néel temperature of CrSBr (∼132 K) as revealed by anomalous Hall effect measurements. The microscopic origin of this behavior is uncovered through cross-sectional magnetic imaging of the domain structure using off-axis electron holography. The results reveal that the asymmetric switching and exchange bias arise from the influence of CrSBr on the domain configuration of FGT, where the in-plane antiferromagnetic state of CrSBr promotes the formation of stripe-like domain structures in FGT with circular rotation of magnetization in the cross-sectional bc plane defined by the easy axes of both FGT and CrSBr. These findings elucidate the mechanism of exchange bias in orthogonally coupled vdW systems and demonstrate a pathway for stabilizing 3D domain structures in ferromagnets through interfacial exchange interactions.

We study current-induced switching of the N\'eel vector in CoO/Pt bilayers to understand the underlaying antiferromagnetic switching mechanism. Surprisingly, we find that for ultra-thin CoO/Pt bilayers electrical pulses along the same path can lead to an increase or decrease of the spin Hall magnetoresistance signal, depending on the current density of the pulse. By comparing the results of these electrical measurements to XMLD-PEEM imaging of the antiferromagnetic domain structure before and after the application of current pulses, we reveal the reorientation of the N\'eel vector in ultra-thin CoO(4 nm). This allows us to determine that even opposite resistance changes can result from a thermomagnetoelastic switching mechanism. Importantly, our spatially resolved imaging shows that regions where the current pulses are applied and regions further away exhibit different switched spin structures, which can be explained by a spin-orbit torque based switching mechanism that can dominate in very thin films.

Two-dimensional van der Waals (vdW) heterostructures are an attractive platform for studying exchange bias due to their defect free and atomically flat interfaces. Chromium thiophosphate (CrPS4), an antiferromagnetic material, possesses uncompensated magnetic spins in a single layer, rendering it a promising candidate for exploring exchange bias phenomena. Recent findings have highlighted that naturally oxidized vdW ferromagnetic Fe3GeTe2 exhibits exchange bias, attributed to the antiferromagnetic coupling of its ultrathin surface oxide layer (O-FGT) with the underlying unoxidized Fe3GeTe2. Anomalous Hall measurements are employed to scrutinize the exchange bias within the CrPS4/(O-FGT)/Fe3GeTe2 heterostructure. This analysis takes into account the contributions from both the perfectly uncompensated interfacial CrPS4 layer and the interfacial oxide layer. Intriguingly, a distinct and non-monotonic exchange bias trend is observed as a function of temperature below 140 K. The occurrence of exchange bias induced by a 'pre-set field' implies that the prevailing phase in the polycrystalline surface oxide is ferrimagnetic Fe3O4. Moreover, the exchange bias induced by the ferrimagnetic Fe3O4 is significantly modulated by the presence of the van der Waals antiferromagnetic CrPS4 layer, forming a heterostructure, along with additional iron oxide phases within the oxide layer. These findings underscore the intricate and complex nature of exchange bias in van der Waals heterostructures, highlighting their potential for tailored manipulation and control.

The exchange bias phenomenon, inherent in exchange-coupled ferromagnetic and antiferromagnetic systems, has intrigued researchers for decades. Van der Waals materials, with their layered structures, offer an ideal platform for exploring exchange bias. However, effectively manipulating exchange bias in van der Waals heterostructures remains challenging. This study investigates the origin of exchange bias in MnPS3/Fe3GeTe2 van der Waals heterostructures, demonstrating a method to modulate nearly 1000% variation in magnitude through simple thermal cycling. Despite the compensated interfacial spin configuration of MnPS3, a substantial 170 mT exchange bias is observed at 5 K, one of the largest observed in van der Waals heterostructures. This significant exchange bias is linked to anomalous weak ferromagnetic ordering in MnPS3 below 40 K. The tunability of exchange bias during thermal cycling is attributed to the amorphization and changes in the van der Waals gap during field cooling. The findings highlight a robust and adjustable exchange bias in van der Waals heterostructures, presenting a straightforward method to enhance other interface-related spintronic phenomena for practical applications. Detailed interface analysis reveals atom migration between layers, forming amorphous regions on either side of the van der Waals gap, emphasizing the importance of precise interface characterization in these heterostructures.

Two-dimensional van der Waals (vdW) heterostructures are an attractive platform for studying exchange bias due to their defect free and atomically flat interfaces. Chromium thiophosphate (CrPS4), an antiferromagnetic material, possesses uncompensated magnetic spins in a single layer, rendering it a promising candidate for exploring exchange bias phenomena. Recent findings have highlighted that naturally oxidized vdW ferromagnetic Fe3GeTe2 exhibits exchange bias, attributed to the antiferromagnetic coupling of its ultrathin surface oxide layer (O-FGT) with the underlying unoxidized Fe3GeTe2. Anomalous Hall measurements are employed to scrutinize the exchange bias within the CrPS4/(O-FGT)/Fe3GeTe2 heterostructure. This analysis takes into account the contributions from both the perfectly uncompensated interfacial CrPS4 layer and the interfacial oxide layer. Remarkably, a distinct and non-monotonic exchange bias trend is observed as a function of temperature below 140 K. Intriguingly, a pre-set field-induced exchange bias suggests that the predominant phase in the polycrystalline surface oxide is ferrimagnetic Fe3O4. Moreover, the exchange bias induced by the ferrimagnetic Fe3O4 is significantly modulated by the presence of the van der Waals antiferromagnetic CrPS4 layer, forming a heterostructure, along with additional iron oxide phases within the oxide layer. These findings underscore the intricate and unique nature of exchange bias in van der Waals heterostructures, highlighting their potential for tailored manipulation and control.

Efficient and reliable electrical writing and reading of the Néel vector in antiferromagnetic insulators is a key prerequisite in view of using this class of materials as active elements in future spintronic devices. Here, we study the current-induced switching of the Néel vector in NiO/Pt and CoO/Pt bilayers. We compare the signal read out electrically, via the spin Hall magnetoresistance effect, with the imaged magnetic domain structure and from this comparison we identify the switching mechanisms that lead to the reorientation of the Néel vector in the thin films.