The high electron mobility for spin‐down channel of two‐dimensional spin‐polarized half‐metallic ferromagnetic <scp>EuSi₂N₄</scp> monolayer

The two-dimensional (2D) monolayer material MoSi₂N₄ was successfully synthesized in 2020[Hong et al., Science 369, 670, (2020)], exhibiting a plethora of new phenomena and unusual properties, with good stability at room temperature. However, MA₂Z₄ family monolayer materials involve primarily transition metal substitutions for M atoms. In order to address the research gap on lanthanide and actinide MA₂Z₄ materials, this work conducts electronic structure calculations on novel 2D MSi₂N₄ (M = La, Eu) monolayer materials by employing first-principles methods and CASTEP. High carrier mobility is discovered in the indirect bandgap semiconductor 2D LaSi₂N₄ monolayer (~5400 cm² V^-1 s^-1) and in the spin (spin-down channel) carrier mobility of the half-metallic ferromagnetic EuSi₂N₄ monolayer (~2800 cm² V^-1 s^-1). EuSi₂N₄ monolayer supplements research on spin carrier mobility in half-metallic ferromagnetic monolayer materials at room temperature and possesses a magnetic moment of 5 μ_B, which should not be underestimated. Furthermore, due to the unique electronic band structure of EuSi₂N₄ monolayer (with the spin-up channel exhibiting metallic properties and the spin-down channel exhibiting semiconductor properties), it demonstrates a 100% spin polarization rate, presenting significant potential applications in fields such as magnetic storage, magnetic sensing, and spintronics.