Half-Metallic Ferromagnetism in UCu2X2 (X = P, As) Zintl Compounds: Exploring the Magnetic Stability, Electronic Structure, Exchange Interactions, and Implications for Next-Generation Storage Technologies

Abstract

The pursuit of half-metallic ferromagnets with 100% spin polarization at room temperature remains an ongoing challenge. This study employs density functional theory to investigate the structural, electronic, and magnetic properties of Zintl compounds UCu₂X₂ (X = P, As). The local density approximation (LDA) and generalized gradient approximation (GGA) have been employed within the full-potential linearized augmented plane wave plus local orbital (FP-LAPW + lo) method as exchange–correlation functionals. Additionally, the GGA + U approach and various versions of the modified Becke-Johnson (mBJ) potential were utilized to obtain more accurate results. Notably, the calculated lattice constants and c/a ratio for UCu₂P₂ are in excellent agreement with experimental values. The results confirm the thermodynamic stability and robust atomic interactions of these compounds. It is discovered that all UCu₂X₂ (X = P, As) Zintl compounds achieve their lowest ground state energy in the FM state as compared to the NM state. Electronic structure calculations reveal that UCu₂X₂ exhibits half-metallic behavior, characterized by 100% spin polarization, an indirect band gap of 0.7 eV, and strong hybridization between X-s/p and U-f/d states. The compounds also display spin gapless semiconducting behavior and double exchange interaction, validating their half-metallic ferromagnetic nature. The ferromagnetism is primarily attributed to the appearance of one 5d-electron outside the final rare earth element’s filled 14-electron 4f shell. The U and Cu atoms contribute most significantly to the total magnetic moment, with minor contributions from interstitial regions. The presence of integer magnetic moments further corroborates the half-metallic ferromagnetic nature of UCu₂X₂, providing clear evidence of this phenomenon. The computed Curie temperatures are 0.0116 × 10⁵ K and 0.0323 × 10⁵ K for UCu₂P₂ and UCu₂As₂, respectively. These findings highlight the potential of UCu₂X₂ for applications in next-generation storage devices and spintronics, offering a promising avenue for further research and development.