High Curie temperatures in Gd-dihalide Janus monolayers

As MoSSe has been successfully synthesized, it is expected that Janus structures would be newly developed as 2D materials with intriguing physical properties. Here, monolayer Janus GdXY (with X/Y = Cl, Br, I), a ferromagnetic semiconductor with a high Curie temperature, is predicted by density functional theory combined with Monte Carlo simulations. The calculations show that the cleavage energies of monolayers 2 H - GdX 2 (X = Cl, Br, I) and GdXY are about 0.21 J / m 2, which are smaller than that of graphene. The Janus GdXY monolayers have semiconducting bandgaps and show in-plane ferromagnetic order with Curie temperatures of 167-181 K. The magnetic moment is as high as 8 μ B/Gd. In addition, GdXY monolayers also have strong Heisenberg exchange interactions in the range of 35-37 meV, which are larger than that of CrI 3. We also find that both of their magnetic anisotropy and Curie temperature can be largely altered by strain. High Curie temperatures and 100% spin polarization make Janus GdXY monolayers good platforms for the research studies of spintronics devices.