Two-dimensional bipolar magnetic semiconductors with high Curie-temperature and electrically controllable spin polarization realized in exfoliated Cr(pyrazine)2 monolayers

Exploring two-dimensional (2D) magnetic semiconductors with room-temperature magnetic ordering and electrically controllable spin-polarization is a highly desirable but challenging task for nano-spintronics. Here, through first-principles calculations, we propose to realize such a material by exfoliating the recently synthesized organometallic layered crystal Li0.7[Cr(pyz)2]Cl0.7·0.25(THF) (pyz=pyrazine, THF=tetrahydrofuran). The feasibility of exfoliation is confirmed by the rather low exfoliation energy of 0.27 J m−2, even smaller than that of graphite. In exfoliated Cr(pyz)2 monolayers, each pyrazine ring grabs one electron from the Cr atom to become a radical anion, and then a strong d-p direct-exchange magnetic interaction emerges between Cr cations and pyrazine radicals, resulting in room-temperature ferrimagnetism with a Curie temperature of 342 K. Moreover, the Cr(pyz)2 monolayer is revealed to be an intrinsic bipolar magnetic semiconductor where electrical doping can induce half-metallic conduction with controllable spin-polarization direction.