Heterostructures*

Exploiting multiferroic BiFeO₃ (BFO) thin films in spintronic devices requires deterministic and robust control of both the internal magnetoelectric coupling in BFO as well as exchange coupling of its antiferromagnetic (AF) order to a ferromagnetic overlayer. Previous reports of exchange coupling in films have utilized approaches based on multistep ferroelectric (FE) switching with multiple FE domains. Because domain walls can be responsible for fatigue, can contain localized charges either intrinsically or via defects, and present issues for device reproducibility and scaling, an alternative approach using a monodomain magnetoelectric state with single–step switching is desirable for practical devices. Here we demonstrate RT, deterministic and robust exchange coupling between monodomain BFO films and a Co overlayer that is “intrinsic” (without domain walls). Direct coupling between AF order in BFO and Co magnetization leads to ~90° in–plane Co moment rotation upon single-step FE switching, reproducible for hundreds of cycles[1]. This has important consequences for useful BFO-based magnetoelectric devices.

[1] Nat. Comm. (in press).