Modulated exchange bias and antisymmetric magnetoresistance at a spin–flop coupled van der Waals interface of FeTe/Fe3GeTe2

We construct a van der Waals heterostructure of FeTe/Fe3GeTe2 (FGT), which presents a spin-orthogonal interface and exchange bias effect. The underlying mechanism of the observed bias field is ascribed to proximity-induced uncompensated interfacial moments in FeTe, which act as effective pinning centers for the magnetization reversal in Fe3GeTe2 and whose configuration is set by the field-cooling and subsequent field-sweep history. Field-sweep history plays an important role in this effect: in asymmetric field-sweep protocols, the bias field shows a clear and systematic trend with the reversing field and can be continuously tuned from −300 to +200 Oe. Interestingly, the effect persists up to about 100 K, well above the Néel temperature of bulk FeTe (∼65 K). These are accompanied by antisymmetric magnetoresistance, arising from the asynchronous reversal of the FGT surface and bulk layers together with interfacial spin-dependent scattering. We attribute the above findings to a spin–flop coupling arising from the FeTe/Fe3GeTe2 interface and the reconfigurable interfacial pinning moments under asymmetric field-sweep protocols. This work provides a new route toward van der Waals spintronic devices based on the reconfigurable exchange bias effect and multi-resistance state functionality.