Coexistence of Altermagnetism and Ferroelectricity in Rhombohedral GaFeO3: A Promising Multiferroic Platform for Spintronics

Abstract

Altermagnetic materials are a distinct class of materials that merge spin splitting in spin-polarized electronic bands, a defining feature of ferromagnets, with an antiparallel spin configuration and zero resultant magnetization, which is typical of antiferromagnets. Herein, we explored the multifunctional properties of polar GaFeO3 and predicted it as a ferroelectric altermagnet with good stability. We obtained a Young’s modulus of 218 GPa for bulk GaFeO3, indicating that it is robust under a mechanical load. In addition, this material has a Pugh’s ratio of 2.4 and Poisson’s ratio of 0.32, indicating its inherent ability to dissipate stress rather than fracturing. The semiconducting polar GaFeO3 exhibits altermagnetic behavior with a spin splitting of ∼65 meV at the valence band. The altermagnet GaFeO3 has a magnetocrystalline anisotropy energy of −5 μeV/unit cell with the easy axis being along the [111] direction. This altermagnet has a Néel temperature (TN) of 402 K. Altermagnet GaFeO3 exhibits a giant spontaneous electric polarization of 103 μC/cm2 with a low switching energy barrier of 0.66 eV per formula unit. Our results predict polar GaFeO3 as a multifunctional ferroelectric altermagnet for next-generation multiferroic device applications.