Dual-tunable polarity reversal of exchange bias in the Fe3GaTe2/O-Fe3GaTe2 heterostructures

The polarity reversal of exchange bias (EB) in two-dimensional (2D) van der Waals magnets remains a significant scientific challenge, yet is highly desirable for advanced spintronic applications. Conventional approaches relying on artificially stacked heterostructures often suffer from weak interfacial coupling and limited tunability. Here, we demonstrate a reversal of the EB polarity in an intrinsically formed Fe3GaTe2/O-Fe3GaTe2 heterostructure achieved through thermal oxidation. This system exhibits a remarkable reversal of the EB polarity with both temperature and magnetic field orientation, alongside robust stability under repeated magnetic cycling. A trilayer magnetic model, comprising a top oxidized layer, an interfacial oxidized region, and a bottom pristine ferromagnetic layer, is proposed to explain the phenomenon, revealing a delicate competition between the Zeeman energy, interlayer exchange, and interfacial coupling. Our work offers a pathway to tune exchange bias in 2D magnets through interface engineering, offering fundamental insights for designing reconfigurable spintronic devices.