Pressure dependent characteristics of spinels AIn₂S₄ (A = Fe, Ni) for spintronic applications: mechanical stable,...

Spintronics is an emerging route for next-generation electronics that exploits spin-polarized materials, typically realized in semiconductors and metal through intrinsic magnetic orderings. In current work, mechanical, structural, thermodynamic, and electronic properties for AIn₂S₄ (A = Fe, Ni) spinels are examined in detail utilizing density functional theory (DFT) calculations. Optimized lattice parameters are 10.53 Å for FeIn₂S₄ and 10.43 Å for NiIn₂S₄, in close agreement with reported experimental values. The formation enthalpies of -0.91 eV for FeIn₂S₄ and -0.80 eV for NiIn₂S₄ indicate that both compounds are thermodynamically stable, with the FeIn₂S₄ phase being comparatively more stable. The elasticity demonstrates mechanical stability and ductility, as shown by Poisson's ratios of 0.29 and 0.30 and B ₀/G values of 2.05 and 2.16 for FeIn₂S₄ and NiIn₂S₄, respectively. Spin-polarized band structures and density of states (DOS) represent half-metallic nature and the bandgap progressively increase as pressure increases from 0 to 4 GPa for spin up channel for both spinels. The computed total magnetic moment of 4µ _B f.u.^-1 for FeIn₂S₄ and 2µ _B f.u.^-1 for NiIn₂S₄ mainly stems from Fe/Ni ions, which is characteristic of ferromagnetic order. Thermodynamic parameters, including entropy and Debye temperature, obtained using the quasi-harmonic Debye model reveal signs of lattice stiffening, phonon softening, and anharmonicity. Overall, these findings confirm that AIn₂S₄ (A = Fe, Ni) spinels possess thermal stability and strong vibrational features, thereby making them suitable candidates for spintronics and magneto-electronic devices.