Origins of ferromagnetism in helium-implanted PdCoO2

Abstract

Magnetic materials that combine strong spin-orbit coupling with ferromagnetism enable interconversion between charge and spin currents as well as stabilization of exotic spin textures, properties that are critical for advancing next-generation spintronic technologies. The metallic delafossite PdCoO2 is a highly conductive, nonmagnetic oxide that resides near a magnetic instability, making it a unique and promising monolithic platform for spin phenomena. Here, we investigate how helium implantation drives PdCoO2 into a magnetic state. Through depth-resolved low-energy muon spin relaxation (LE-μSR) measurements, ion implantation simulations, and first-principles calculations, the defects responsible for the emergent magnetism are identified. While oxygen Frenkel pairs, palladium Frenkel pairs, and interstitial helium contribute weakly, cobalt Frenkel pairs play the dominant role in generating magnetism. In addition, postimplantation annealing reveals distinct thermal windows for defect recombination, confirming the elemental specificity of cation-related defects. These findings establish defect engineering via ion implantation as a powerful route to controllably induce magnetism in PdCoO2. The combination of strong spin-orbit coupling, selectively tunable magnetism, and ultrahigh conductivity positions helium-implanted PdCoO2 as a unique platform for monolithic spintronic device integration, with implications for low-power magnetic memory and unconventional logic applications.