First-principles insights into tailoring structural, magnetic and electronic properties of Co2−xNixNbSn Heusler alloys

This study explores a comprehensive first-principles investigation into the structural, magnetic, and electronic properties of Co${}_{2-x}$Ni${}_x$NbSn Heusler alloys using density functional theory. Systematic Ni doping in the L2₁ cubic structure induces lattice expansion due to Ni’s larger atomic radius and drives a transition from ferromagnetic Co₂NbSn to paramagnetic Ni₂NbSn. Structural analysis reveals that Co-rich compositions ($x<$ 1.5) exhibit martensitic instability, undergoing tetragonal and orthorhombic distortions, while Ni-rich compounds ($x\ge$ 1.5) stabilize in a cubic phase. Magnetic measurements show a progressive reduction in magnetic moment with Ni substitution, vanishing entirely for $x\ge$ 1.75, signaling a magnetic ground-state transition. Spin-polarized total density of states (DOS) analyses demonstrate a high DOS at the Fermi level in Co-rich compounds linked to Jahn–Teller distortions and robust ferromagnetism, that declines with increasing Ni content. In Ni₂NbSn, a Van Hove singularity near the Fermi level suggests potential superconductivity. These findings underscore the tunable multifunctional nature of Co${}_{2-x}$Ni${}_x$NbSn alloys, making them promising candidates for applications in spintronics, magnetic devices, and superconducting technologies.