Chalcogen doping effect on the insulator-to-metal transition in GdPS

Topological semimetals offer a rich platform for exploring massless fermion physics and realizing exotic properties with potential technological applications. GdPS, a magnetic semiconductor derived from the nodal-line semimetal ZrSiS family, exhibits a field-induced insulator-to-metal transition driven by exchange splitting. This transition is accompanied by an unusual, isotropic, and gigantic negative magnetoresistance, attributed to negligible magnetic anisotropy resulting from the weak spin-orbit coupling of half-filled Gd³⁺ 4 f orbitals and light S atoms. In this work, we investigate Se substitution, which is expected to enhance spin-orbit coupling. Indeed, we observe slightly increased magnetic anisotropy in magnetotransport. Moreover, Se substitution suppresses the field-induced insulator-to-metal transition, likely due to an enlarged band gap that demands a higher exchange splitting to close. These findings provide deeper insights into the interplay between spin-orbit coupling, magnetic anisotropy, and transport behavior in GdPS, offering guidance for future materials design for desired functionalities. • Unusual isotropic and gigantic negative magnetoresistance in GdPS arises from insulator-to-metal transition caused by band modification due to f - d exchange splitting. The negligible magnetic anisotropy resulting from the weak spin-orbit coupling of half-filled Gd³⁺ 4 f orbitals and light S atoms, creating isotropy field response. • Chalcogen substitution in GdPS enhances spin-orbit coupling, enhancing the magnetic anisotropy and magnetoresistance anisotropy. • Findings provide deeper insight into the interplay between spin-orbit coupling, magnetic anisotropy, and transport behavior in GdPS.