The high electron mobility for spin-down channel of two-dimensional spin-polarized half-metallic ferromagnetic EuSi 2 N 4 monolayer.

The two-dimensional (2D) monolayer material MoSi 2 N 4 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, MA 2 Z 4 family monolayer materials involve primarily transition metal substitutions for M atoms. In order to address the research gap on lanthanide and actinide MA 2 Z 4 materials, this work conducts electronic structure calculations on novel 2D MSi 2 N 4 (M = La, Eu) monolayer materials by employing first-principles methods and CASTEP. High carrier mobility is discovered in the indirect bandgap semiconductor 2D LaSi 2 N 4 monolayer (~5400 cm 2  V -1  s -1 ) and in the spin (spin-down channel) carrier mobility of the half-metallic ferromagnetic EuSi 2 N 4 monolayer (~2800 cm 2  V -1  s -1 ). EuSi 2 N 4 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 EuSi 2 N 4 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.