Spin-dependent transport in Fe${}_3$GaTe${}_2$ and Fe${}_n$GeTe${}_2$ ($n$=3-5) van der Waals ferromagnets for magnetic tunnel junctions

Abstract

We present a systematic first-principles investigation of linear-response spin-dependent quantum transport in the van der Waals ferromagnets Fe${}_3$GeTe${}_2$, Fe${}_4$GeTe${}_2$, Fe${}_5$GeTe${}_2$, and Fe${}_3$GaTe${}_2$. Using density functional theory combined with the non-equilibrium Green's function formalism, we compute their Fermi surfaces, transmission coefficients, and orbital-projected density of states. All compounds exhibit nearly half-metallic conductance along the out-of-plane direction. This is characterized by a finite transmission coefficient for one spin channel and a gap in the other, resulting in spin polarization values exceeding 90$\%$ in the bulk. Notably, Fe${}_3$GaTe${}_2$ displays the ideal half-metallic behavior, with the Fermi energy located deep in the spin-down transmission gap. We further show that this high spin polarization is preserved in bilayer magnetic tunnel junctions, which exhibit a large tunnel magnetoresistance of the order of several hundred percent. This findings underscore the promise of these materials, and in particular of Fe${}_3$GaTe${}_2$, for spintronics applications.

11 pages, 5 figures