Coexistence of ferromagnetism and cost density waves in monolayer LaBr2

Cost density waves (CDWs), a standard phenomenon of periodic lattice distortions, typically suppress ferromagnetism in two-dimensional (2D) supplies, hindering their magnetic functions. Right here, we report a novel CDW that generates 2D ferromagnetism as an alternative of suppressing it, by means of the formation of interstitial anionic electrons because the cost modulation mechanism. By way of first-principles calculations and a low-energy efficient mannequin, we discover that the extremely symmetrical monolayer LaBr₂ undergoes a 2 × 1 CDW transition to a magnetic semiconducting T′ part. Concurrently, the delocalized 5d¹ electrons of La in LaBr₂ redistribute and accumulate throughout the interstitial area within the T′ part, forming anionic electrons, also referred to as 2D electride or electrene. The strongly localized nature of anionic electrons promotes a Mott insulating state and full spin-polarization, whereas the overlap of their prolonged tails yields ferromagnetic direct trade between them. Such transition introduces a brand new magnetic type of CDWs, providing promising alternatives for exploring novel basic physics and superior spintronics functions.