Theoretical analysis of double perovskite A2HfNiO6 (where A = Ba, Ca, and Sr) for structural, elastic optical, electronic, thermoelectric and magnetic properties for spintronics applications

This work comprises a thorough investigation of the structural, optical, electronic, thermoelectric, and magnetic properties of the double perovskite (DP) cubic compound A₂HfNiO₆ (A = Sr, Ca, Ba). The electronic properties of these DPs were revealed with the assistance of the band structure, an indirect band gap with a half-metallic semiconductor nature was proposed; the band gap of Ba₂HfNiO₆, Sr₂HfNiO_6, and Ca₂HfNiO₆ are 3.70, 2.91 and 2.42 eV respectively. The mechanical stability of these compounds was confirmed by Born stability criteria. The optical behavior was assessed using different parameters, including the optical conductivity(σ), the absorption coefficient(α), the reflectivity(R), and the loss parameter(L). Furthermore, the thermal properties were explored utilizing the electrical conductivity (σ/τ), charge carrier concentrations (n), Seebeck coefficient (s), specific heat capacity (C_v), magnetic susceptibility (χ), thermal conductivity (K_e/t) and power factor (PF) parameters. These values were calculated with the help of the BoltzTraP program combined with the WIEN2k, utilizing the PBE-GGA approximation in density functional theory. The presence of orbital hybridization contributed to the appearance of magnetic moments in these two components down spin (↓) and up spin (↑). Therefore, the magnetic moment of the studied materials Ca₂HfNiO₆, Sr₂HfNiO₆, and Ba₂HfNiO₆ is 3.99990 µB, 4.00001 µB, and 4.00002 µB respectively. For spintronic applications, double perovskite oxides Ca₂HfNiO₆, Sr₂HfNiO₆, and Ba₂HfNiO₆ may be regarded as acceptable materials since they function as half-metals and have the required magnetic saturation so, these materials could be used in the production of magnetic storage devices and magnetic circuits.