Tuning the magnetic and electronic properties of two-dimensional electrides by forming cationic Janus compounds

Conventional two-dimensional (2D) Janus materials are featured by the different anions on the two sides of the structures. In this work, we report a new type of Janus structures, Janus electrenes with different cation layers. By substituting one of the two zirconium cation layers in Zr2Cl2 with group I to III elements, we generated nine Janus 2D materials ZrXCl2, where X = Na, K, Rb, Ca, Sr, Ba, Sc, Y or La. The phonon spectra demonstrate the dynamical stability of ZrScCl2, ZrYCl2 and ZrCaCl2, confirming the feasible formation of cationic Janus electrenes. Interestingly, the different groups of Janus structures have dramatically different electronic and magnetic properties. While the substitution of group III elements introduces ferromagnetic anionic electrons to the ZrXIIICl2 systems, ZrXIICl2 are semiconductors with band gaps of around 0.2 eV with flat valence bands (band width from 175 to 234 meV), and ZrXICl2 are ferromagnetic half-metals. Our results open up a new dimension of freedom to effectively tune the electronic and magnetic properties of electrenes, paving the way for their novel applications.