Ion irradiation and implantation modifications of magneto-ionically induced exchange bias in Gd/NiCoO

TL;DR

This study investigates how helium ion irradiation and oxygen implantation modify the exchange bias in Gd/NiCoO heterostructures through lattice and interfacial magnetic changes, offering a new way to control magneto-ionic effects in spintronics.

Contribution

It demonstrates the effects of ion irradiation and implantation on magneto-ionic exchange bias, revealing how lattice and interfacial modifications influence magnetic properties in Gd/NiCoO.

Findings

Low fluence He+ increases interfacial magnetic moments.

High fluence He+ suppresses exchange bias.

Oxygen implantation causes lattice expansion and phase segregation.

Abstract

Magneto-ionic control of magnetic properties through ionic migration has shown promise in enabling new functionalities in energy-efficient spintronic devices. In this work, we demonstrate the effect of helium ion irradiation and oxygen implantation on magneto-ionically induced exchange bias effect in Gd/Ni$_{0.33}$Co$_{0.67}$O heterostructures. Irradiation using $He^+$ leads to an expansion of the Ni$_{0.33}$Co$_{0.67}$O lattice due to strain relaxation. At low He+ fluence ($\leq$ 2$\times$10$^{14}$ ions cm$^{-2}$), the redox-induced interfacial magnetic moment initially increases, owing to enhanced oxygen migration. At higher fluence, the exchange bias is suppressed due to reduction of pinned uncompensated interfacial Ni$_{0.33}$Co$_{0.67}$O spins. For oxygen implanted samples, an initial lattice expansion below a dose of 5$\times$10$^{15}$ cm$^{-2}$ is subsequently dominated at higher dose by a lattice contraction and phase segregation into NiO and CoO-rich phases, which in turn alters the exchange bias. These results highlight the possibility of ion irradiation and implantation as an effective means to tailor magneto-ionic effects.