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 ${\mathrm{CrBr}}_{3}$ 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 ${\mathrm{CrBr}}_{3}$ stands for experimental verification and presents enormous new possibilities for spintronic and magnetoelectric quantum devices based on atomically thin crystals.