Room-temperature ferromagnetism in two-dimensional CrBr3

Abstract

High-temperature ferromagnetism and its control in ultrathin materials are of critical interest in disruptive quantum technologies. However, intrinsic ferromagnetic ordering in recently discovered two-dimensional materials is limited to cryogenic temperatures due to fundamental spin fluctuation in reduced dimensions. While chromium trihalides order below 45 K, we report a dramatic manipulation of long-range ferromagnetic order above room temperature in CrBr3 monolayer predicted within the first-principles long-range Heisenberg XXZ model. Gate-induced charge carrier doping externally modulates various magnetic interactions in the Mott insulating monolayer, and a nontrivial magnetic phase diagram emerges. Under varied hole density, the monolayer remains ferromagnetic with Curie temperature increasing monotonically, while electron doping triggers a complex evolution of magnetic phases. The microscopic details are investigated, and the high-temperature ferromagnetism is attributed to the substantial increase in effective ferromagnetic exchange and magnetic anisotropies under an experimentally attainable hole density. Such electrically controlled ferromagnetism in CrBr3 stands for experimental verification and presents enormous new possibilities for spintronic and magnetoelectric quantum devices based on atomically thin crystals.