Emergent Global-Pinning Exchange Bias in van der Waals Magnetic Heterostructures

As magnetoresistive random access memory (MRAM) technology becomes increasingly vital for emerging applications, such as artificial intelligence, the development of cost-effective and miniaturized solutions is essential. van der Waals (vdW) magnets, which can be vertically stacked with various functional blocks, offer promising potential to enhance the performance and scalability of memory devices. Nevertheless, the need for perfect alignment between adjacent layers and finite local interactions at the interfaces often complicates device architectures and leads to high power consumption. Addressing these challenges, a new device configuration with partial overlap while maintaining the global effect would be a promising scheme. Here, using Fe₃GeTe₂/MnBi₂Te₄ (FGT/MBT) as a paradigm, the global-pinning exchange bias (GPEB) effect is successfully achieved with a horizontal pinning distance approaching 100 µm. Specifically, once stacking a small-area MBT on FGT, the entire FGT is fully biased due to magnetic couplings inherent to vdW magnets, as confirmed by the theoretical model. Interlayer coupling and coverage ratio provide additional degrees of freedom to manipulate the GPEB. Remarkably, this emergent GPEB effect is prevalent across vdW heterostructures composed of various vdW magnets. This work expands design flexibility and offers strategies for constructing new in-memory computing devices, opening exciting possibilities for future spintronic applications.