Flat band induced room-temperature ferromagnetism in two-dimensional systems

The remarkable and fascinating properties of two-dimensional materials have\nraised them to the rank of most promising candidates for technological\napplications. In particular, the possibility of long-range ferromagnetic order\nin 2D materials is generating a growing excitement. Here, we demonstrate that\nflat bands (FBs) may pave the way to room temperature ferromagnetism in 2D\ncompounds. Indeed, the magnetic exchanges between localized spins are largely\ndominated by the FB-FB contribution. This contribution is ferromagnetic and\nscales linearly with the local coupling, thus leading to cross-over\ntemperatures (ferromagnetic phase/ paramagnetic phase) higher by an order of\nmagnitude than those currently reported in experiments. Cross-over temperatures\nas high as $600~ K$ could be reached in micrometer-sized FB systems.\n