Effect of the Lattice-distortion on the Electronic Structure, Magnetic Anisotropy, and Hall Conductivities of the CoFeCrGa Spin Gapless Semiconductor: A First-Principles Study

Abstract

Spin gapless semiconductors (SGSs), novel quantum materials, are notable for their tunable spin-transport properties. Considering that the SGS materials might have an invariably deformed lattice upon integration into devices, and given that the SGS nature is highly sensitive to external factors, the impact of lattice distortions on the different physical properties of CoFeCrGa SGS alloy has been investigated using density functional theory calculations. For lattice distortions, the uniform strain corresponding to $-6\% \leq \Delta V / V_0 \leq 6\% \quad (a: 5.60\text{-}5.83~\text\r{A})$, and the tetragonal distortion corresponding to $0.8 \leq c/a \leq 1.2 \quad (a: 5.38\text{-}6.16~\text\r{A},~c: 4.92\text{-}6.45~\text\r{A})$ are modelled. All uniformly strained CoFeCrGa structures are found to display SGS character, magnetic isotropy, small anomalous Hall conductivity (AHC), and small spin Hall conductivity (SHC) - closely resembling those of the ideal CoFeCrGa structure. In contrast, the tetragonally deformed structures display nearly half-metallic behavior with very high spin polarization, very large magnetic anisotropy ($ \sim 10^6~\mathrm{J/m^3}$), and very large AHC ranging from ($ -215 \text{ to } 250~\mathrm{S/cm} $) depending on the axial ratio of the distorted structure. The SHC, however, does not change significantly under tetragonal distortion and remains nearly of the same order as that of the Y-I ordered structure. In summary, these findings demonstrate that CoFeCrGa displays favorable spintronic properties even under lattice distortions, underscoring its potential for next-generation spintronic applications.