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

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/Ni0.33Co0.67O heterostructures. Irradiation using He + leads to an expansion of the Ni0.33Co0.67O lattice due to strain relaxation. At low He + fluence (≤2×10 ions cm), 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 Ni0.33Co0.67O spins. For oxygen implanted samples, an initial lattice expansion below a dose of 5×10 cm 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.