Integrating Antiferromagnetic/Ferromagnetic Heterojunction in Van Der Waals Fe_{1+ y}Te Film With Gradient Fe Doping

Manipulating heterojunction architecture in van der Waals (vdW) magnets plays a significant role in developing exotic low-dimensional spintronic physics and technological innovations in quantum computing. However, the conventional heterostructure strategy to engineer a vdW device through complicated and cumbersome stacking strategies is facing a high fabrication cost. Tailoring broken time-reversal symmetries to integrate a distinct magnetic order into a vdW system, by only employing a simplified geometry and the advantage of unique components, currently remains highly challenging. In this work we propose the use of a gradient doping of magnetic atoms in bicollinear antiferromagnetic (AFM) parent vdW magnet to fabricate an AFM/ferromagnetic (FM) heterojunction in a single Fe_{1+ y}Te film, which enables an exchange bias (EB) effect. We demonstrate the emergence of robust FM order and an EB effect in a vdW Fe_1+yTe film. This originates from heavy Fe doping in the interfacial layers and the breaking of symmetry in the bicollinear AFM order within the lightly doped layers away from the interface. This work not only opens a new avenue for manipulating AFM/FM heterojunction in a single parent vdW system but also provides new insights into understanding the production of the EB effect on the bicollinear AFM vdW device platform.