Evaluation of pressure induced physical and magnetic properties of A3CrO4 (A = Mg, Ca, Sr) alkali–metal oxides for spintronics applications via DFT

Abstract

The present study employs density functional theory (DFT) within the CASTEP framework to systematically investigate the pressure-tunable structural, electronic and magnetic properties of A₃CrO₄ (A = Mg, Ca, Sr) alkali–metal oxides using GGA-PBE, GGA+U and GGA-PBEsol functionals. Structural optimization confirms that all A₃CrO₄ (A = Mg, Ca, Sr) compounds crystallize in the cubic P3m space group, with ferromagnetic (FM) ordering consistently more stable than non-magnetic (NM) states across the entire pressure range of 0–30 GPa. Mg₃CrO₄ and Ca₃CrO₄ exhibit robust FM ground states with total magnetic moments of +4.0 to –4.1µ_B maintaining half-metallicity under hydrostatic pressures up to 30 GPa. In contrast, Sr₃CrO₄ undergoes a pressure-induced magnetic phase transition, with its magnetic moment reversing sign at 20–30 GPa, indicating a shift toward antiferromagnetic (AFM) or ferrimagnetic ordering. Elastic constant analysis confirms dynamic stability across the entire pressure range (0–30 GPa). While Mg₃CrO₄ remains brittle under compression, Ca₃CrO₄ and Sr₃CrO₄ exhibit pressure-induced ductility transitions, transforming from brittle to ductile behavior at higher pressures. Electronic structure calculations reveal persistent half-metallicity, with spin-down channels retaining wide band gaps and spin-up channels displaying metallic behavior. The application of Hubbard corrections (GGA+U) further validates the robustness of the electronic properties. The average sound velocity, Debye temperature, Debye frequency, melting temperature and Gruneisen parameter were analyzed under pressures of up to 30 GPa. Mg₃CrO₄ and Ca₃CrO₄ show a steady increase in sound velocity, Debye temperature, and frequency, indicating lattice stiffening, stronger bonding and enhanced thermal stability. In contrast, Sr₃CrO₄ exhibits anomalous behavior, with values rising up to 20 GPa but slightly decreasing at 30 GPa, consistent with its pressure-induced magnetic reversal. Melting temperatures increase significantly for all compounds, confirming their suitability for high-temperature and high-pressure applications. The interplay between pressure and functional analysis in these Cr-based compounds provides valuable insights for advancing spintronics and functional materials design.