He-doping For Materials Design: Controlling Emergent Magnetism in PdCoO₂

Helium doping has recently emerged as a powerful means to engineer strain and emergent functionality in complex oxides without introducing long-range disorder. Using first-principles calculations, we reveal how helium doping drives magnetism in the nonmagnetic, metallic delafossite PdCoO₂ by modifying local bonding and electronic structure. We found that while interstitial helium and oxygen Frenkel pairs contribute weakly, cation (Pd/Co) Frenkel defects dominate by locally distorting the lattice and redistributing charge. Doped helium stabilizes these defects by impeding recombination, resulting in persistent in-plane strain and metastable magnetic clusters. Thus, helium doping induces magnetic order in correlated oxides by controlling the lattice geometry and defect energetics. Theoretical predictions will be verified through depth-resolved muon spectroscopy and SRIM simulations, offering a defect-engineering route for tunable magnetism and next-generation oxide spintronics.