The induction of half-metallicity and enhanced ferromagnetism in a Cr2Ge2Te6 monolayer via electron doping and alkali metal adsorption

Abstract

Two-dimensional (2D) ferromagnetic half-metals hold tremendous potential for use in nanoelectronics and spintronic devices. However, their experimental realization remains a big challenge. In this article, we study electron- and hole-doping effects on a 2D Cr₂Ge₂Te₆ (CGT) monolayer via performing first-principles calculations to investigate its electronic and magnetic properties. Electron-doping has tremendous effects both on the electronic and the magnetic properties. The results show that electron-doping not only induces half-metallicity but it also enhances magnetism in the CGT monolayer. Furthermore, it greatly increases the ferromagnetic stability of the CGT layer. In addition, we manipulated the electron-doping effects via the adsorption of alkali and alkaline-earth metals. The alkali metals act like dopants. Due to charge-transfer, the Fermi level is pushed up, allowing the spin-up channel to conduct while the spin-down channel remains insulating. The half-metallicity is robust, as it does not depend on the adatom concentration. However, the adsorption energy gets reduce with an increase in the concentration of adatoms. In this scenario, the adsorbates tend to repel each other in order to avoid agglomeration, thus leading to a more stable system configuration. More importantly, the local magnetic moment is enhanced because adsorption increases the magnetism. In addition, hydrogen adsorption modifies the band gap at different concentrations but it reduces the magnetic moment of the CGT monolayer.