Comprehensive first-principles study of structural, electronic, magnetic, elastic, ferro-piezoelectricity, thermodynamic, and thermoelectric properties of hexagonal GaMnO3 perovskite for multiferroic applications

Abstract

In this work, we present a comprehensive first-principles investigation of the structural, electronic, magnetic, elastic, ferro-piezoelectric, thermodynamic, thermoelectric, and vibrational properties of hexagonal GaMnO₃ perovskite using density functional theory (DFT). Structural optimization confirms the stability of the polar P6₃c phase, which exhibits a half-metallic ground state with robust ferromagnetic ordering. The electronic structure reveals metallic behavior in the spin-up channel and a wide band gap in the spin-down channel, confirming the half-metallic character. Magnetic analysis shows strong Mn-derived local moments and significant exchange interactions, favorable for spintronic applications. Elastic constants satisfy the Born stability criteria, indicating mechanical stability with ductile behavior and anisotropy consistent with layered hexagonal oxides. Piezoelectric and ferroelectric analyses demonstrate strong spin-dependent polarization and notable electromechanical coupling, highlighting the potential for multifunctional device integration. Thermodynamic calculations reveal stable heat capacity, entropy, and Debye temperature trends across a broad range of temperatures and pressures, while thermoelectric calculations yield nearly isotropic transport with a figure of merit close to unity, suggesting promising thermoelectric efficiency. Phonon dispersion curves show no imaginary frequencies, confirming dynamical stability, with vibrational modes distributed into low-frequency cation vibrations, intermediate MnO₅ distortions, and high-frequency oxygen stretching. These results establish GaMnO₃ as a mechanically, thermodynamically, and dynamically stable multiferroic candidate with coupled ferroic orders and multifunctional potential in spintronic, piezoelectric, and energy-related applications.