Magneto-Ionic Control of Heterostructures and Interfaces*

Magneto-ionic approaches for modifying ion distributions in metal/oxide heterostructures offer exciting potentials to control material properties. Our recent studies show that such magneto-ionic effect, even though initiated at metal/oxide interfaces, can extend deep into the rest of the oxide films and drastically tailor their physical properties [1-4].

In antiferromagnetic systems, we have previously demonstrated a controllable positive exchange bias in GdFe/NiCoO [1], and that the oxygen migration can be reversibly driven by an electric field [2]. Recently, we have observed a strong exchange bias in Gd/NiCoO due to the magneto-ionic effect, above the Gd T_c. After electric biasing, up to 35% enhancement of the exchange bias is observed, which can be reset by field-cooling.

In studies of cuprates, we show a simple, scalable approach to tune superconductivity [4]. A thin Gd layer (up to 20 nm) deposited onto epitaxial YBCO films (100nm), is found to leach oxygen from deep within the YBCO and suppress the superconductivity. These effects arise from the combined impact of redox-driven electron doping and modification of the YBCO microstructure.

In ferromagnets chemisorbed with submonolayer oxygen, we have observed strong DMI induced by chemisorption at room temperature. The sign of this DMI and its surprisingly large magnitude are derived by examining the oxygen coverage dependent evolution of domain wall chirality. The large induced DMI has enabled direct writing of magnetic skyrmions.

Our findings demonstrate an effective solid-state ionic approach to control a wide variety of magnetic functionalities, opening up possibilities for electric gating.

[1]. Gilbert, et al, Nat. Commun., 7, 11050 (2016).
[2]. Gilbert, et al, Nat. Commun., 7, 12264 (2016).
[3]. Gilbert, et al, Phys. Rev. Mater. 2, 104402 (2018).
[4]. Murray, et al, arXiv: 1911.07275.