films*

The metallic delafossite PdCoO₂, which is among the most conductive materials, is an outstanding candidate for studying the electronic behaviors of layered triangular lattice oxides. It was previously found that a simple hydrogen annealing procedure reduces this oxide, which leads to the emergence of magnetism with perpendicular magnetic anisotropy (PMA) and exhibits sign-tunability of anomalous Hall effect (AHE). We show that this effect is dependent on the film thickness. Beyond a critical thickness of 25 nm, the PMA changes to in-plane anisotropy and the sign-tunability of AHE is also inhibited. Extensive analysis of longitudinal and Hall resistance suggests that microscopic changes induced by hydrogen annealing leads to the changes in AHE.