Robustness of Half‐Metallicity and Spin‐Dependent Transport in Defective Co ₂ HfSn and Co ₂ ZrSn Heusler Alloys

The electronic structure and spin‐dependent transport properties of pristine and defective Co 2 HfSn and Co 2 ZrSn Heusler alloys are investigated by first‐principles calculations. Co vacancies, anti‐site substitutions, atomic swaps, and double anti‐sites configurations are considered to assess their impact on half‐metallicity and transport behavior. The pristine compounds exhibit robust half‐metallic ferromagnetism with 100% spin polarization and a magnetic moment of 2.00 μ B per formula unit. Co vacancies preserve the half‐metallic character, whereas anti‐site and swap defects introduce localized states in the minority‐spin gap, leading to spin depolarization. Energy‐averaged descriptors ( P avg , M window , N avg ) are introduced to account for thermally accessible states near the Fermi level. Spin‐resolved transport calculations at fixed carrier concentration reveal that vacancy defects have a minor impact on transport, while substitutional and swap defects promote a more metallic regime and reduce spin selectivity. These results provide clear guidelines for defect engineering in Co‐based Heusler alloys and support their potential for spin‐filtering and spin‐caloritronic applications.