Electrical Transport Measurements of Metallic PdFe_xCo_1–xO₂ and PdCr_xCo1–_xO₂ Delafossite Solid Solutions with Varying Concentration of Unpaired Sp

PdCoO₂ with a delafossite structure has emerged as a prominent material in condensed matter physics and materials science, prized for its high conductivity. Another delafossite material, PdCrO₂, presents a metallic nature but shows antiferromagnetic (AFM) order at low temperature. Compared to PdCoO₂, PdCrO₂ has unpaired electrons in the CrO₂ layer. We are investigating the effect of unpaired electrons on the magnetic properties of these metallic delafossite materials by creating epitaxial films with solid solutions of a transition metal with no unpaired electrons (Co³⁺) with transition metals with unpaired electrons (Fe³⁺ and Cr³⁺), i.e., PdFe_xCo_1–xO₂, PdCr_xCo_1–xO₂, enabling the concentration of unpaired electrons to be continuously varied. Molecular beam epitaxy (MBE) is employed to precisely control the thin film growth of these solid solutions.
Our PdCrO₂ film shows an AFM peak in dρ/dT at low temperature, similar to that of PdCrO₂ single crystals. On the other hand, the PdFe_xCo_1–xO₂ films (0 ≤ x ≤ 0.2) present a dip at around 20 K. Moreover, our PdCr_xCo_1–xO₂ films show similar transport behaviors to the PdFe_xCo_1–xO₂ films, distinct from either pure PdCrO₂ or PdCoO₂ films. This raises questions about the disruption caused by the Cr-Co interaction to the AFM order in the pure CrO₂ layer. In this presentation, we present our quantitative analysis of the Cr-Co interaction in PdCr_xCo_1–xO₂ films with various chromium concentrations (0 ≤ x ≤ 1). Our findings provide new insights into tuning magnetic properties through targeted solid solutions that introduce unpaired electrons into delafossite materials.