Dilute Magnetic Moments and their Influence on Electronic Transport in Single-Crystal PdCo_1-xCr_xO₂

Metallic delafossites are under intense current study due to unique electronic properties, including record-high oxide conductivities in the 2D Pd and Pt layers of their structures. Our recent work [1] reported a chemical vapor transport (CVT) approach to crystal growth of PdCoO₂, elucidating a sublattice purification mechanism underlying the record low-temperature conductivity of these materials. Here, dilute Cr substitution is studied in CVT-grown PdCo_1-xCr_xO₂ (0 ≤ x ≤ 0.047), characterized via X-ray diffraction, spectroscopy, transmission electron microscopy, magnetometry, transport, and specific heat. Structural characterization indicates uniformly distributed Cr, consistent with near-ideal paramagnetism in magnetometry. Confirming the sublattice purification concept, increasing x by a factor of 100 (in the Co-O layers) leads to a factor of only ~3 increase in residual resistivity (in the Pd layers). Intriguingly, a Kondo effect also arises in transport, suggesting interactions between Pd-layer conduction electrons and Cr local moments in Co-O octahedral layers.

[1] Zhang et al., arXiv:2308.14257 (2023).