Vacuum barrier engineering tunneling magnetoresistance in van der Waals Fe5GeTe2 homojunctions

The atomically thin and flexible characteristics of 2D van der Waals (vdW) materials allow for high-quality, tunable multilayer stacking. This gives rise to pure physical phenomena and broad application prospects in spintronics. Recently, very high tunneling magnetoresistance (TMR) has been obtained in all-vdW magnetic tunnel junctions (MTJs), indicating the potential of vdW materials for non-volatile spintronic memory applications. Here, we report an all-vdW MTJ device based on an Fe5GeTe2 homojunction, using a vacuum layer as the tunneling barrier. The TMR value first increases and then decreases as the thickness of the vacuum barrier layer grows, with a maximum TMR value reaching up to 68.4%. We also propose an in-plane electron momentum (k∥) resolved tunneling model specifically for TMR calculation in ferromagnetic homojunctions, which can well explain our experimental results. The simplified bilayer-MTJ structure offers attractive possibilities for spin-based memory, logic, and neuromorphic computing.