Temperature-dependent magnetoresistance and Pauli magnetic susceptibility in TM-doped Fe(OH)2 LDHs: DFT insight for advanced water splitting and energy devices

In recent years, significant advances have been achieved by regulating photocatalytic performance through electron spin manipulation and temperature control in solar-driven photoelectrochemical water splitting. Density functional theory (DFT) calculations are employed to elucidate the coupling among spin-dependent electronic characteristics, photoelectrode, temperature-dependent magnetoresistance, and Pauli magnetic susceptibility in layered double hydroxides (LDH) with intercalated water, doped with 3 d transition-metal guests (Co, Ni, Pt, Re, Rh, Ru, and V). The results indicate that V-doped Fe-LDH exhibits stable n -type semiconducting behavior, suggesting its suitability as a photoanode material. In contrast, pristine [Fe(OH) 2 ] 2 :H 2 O and systems doped with Ni, Co, Rh, Ru, Re, or Pt reveal p -type semiconducting behavior, making them suitable for photocathode applications. The pristine compound and the Co-, Re-, Ru-, and Pt-doped structures exhibit an atypical increase in magnetoresistance with rising temperature. A comparable reduction in magnetoresistance has been reported for overoxidized magnetic tunnel junctions, and ferromagnetic-to-helimagnetic transition. By regulating the electron transfer pathway, magnetoresistance analysis reveals the apparent oxygen evolution reaction (OER) activity and improves photoinduced charge separation efficiency, thereby achieving significantly enhanced hydrogen production under visible light. Meanwhile, for Fe-based systems doped with Co, Re, and Ru, the Pauli magnetic susceptibility exhibits a magnetic phase transition from an antiferromagnetic to a ferromagnetic state at the Néel temperature. The calculated Néel temperatures are T N = 1 . 80 K for Fe-Co and T N = 1 . 20 K for both Fe-Re and Fe-Ru systems. It is plausible that the Pauli magnetic susceptibility contributes to the enhanced activity toward oxygen evolution. Within this temperature range, the Co-, Re-, and Ru-doped structures also show a tendency toward ferromagnetic ordering as temperature increases. These insights provide guidance for the design of materials and devices operating under elevated thermal conditions, including electrochemical systems, heat spreaders, integrated thermal-electrical management components, and energy storage applications. • Spin-dependent transport and photoelectrode type in 3d metal–doped Fe-LDHs correlate with dopant and temperature. • V-doped Fe-LDH exhibits robust n-type conductivity, ideal for photoanode applications. • Pristine and Ni-, Co-, Rh-, Ru-, Re-, Pt-doped Fe-LDHs show p-type behavior suitable for photocathodes. • Low-temperature magnetoresistance in doped Fe-LDHs mimics overoxidized magnetic tunnel junctions. • Pauli susceptibility reveals antiferromagnetic–paramagnetic transition at Néel temperature in Co-, Re-, Ru-doped systems.