Graphene-Like LinearDispersion Spin-Gapless FerromagneticHalf-Metallic in Two-Dimensional DJ Phase Perovskite Cs₂M₂X₈

Due to their unique electronic properties, rich regulatory properties, and excellent magnetic response characteristics, two-dimensional (2D) magnetic materials show tremendous application potential in logic computation, information storage, and other fields. However, their practical application has been severely limited by spin polarizability, low Curie temperature, and low magnetic anisotropy in the realm of room-temperature electronics. Therefore, to achieve intrinsic room-temperature ferromagnetism, finding and designing new 2D ferromagnetic materials with robust magnetic order and high Curie temperature has become a research hotspot. Here, through first-principles calculations, the 2D DJ phase Cs₂M₂X₈ (M = Fe, Co, Mn, X = Br, Cl) perovskite is screened by introducing magnetic elements at the M position, and it is found that the 2D Cs₂Mn₂Br/Cl₈ exhibits ferromagnetic half-metal properties. Its two spin channels display zero-gap metallicity and large-band gap semiconductor characteristics, with each Cs₂Mn₂Br/Cl₈ primitive cell having a large magnetic moment of 8 μB. Additionally, the Fermi surface exhibits 100% spin polarization, with neighboring bands displaying graphene-like linear dispersion and an ultrahigh Fermi velocity of 4.73 × 10⁵ m/s, as well as a nodal line semimetal Fermi surface structure, demonstrating excellent transport characteristics in a single spin channel. Moreover, the Curie temperature of the 2D Cs₂Mn₂Br₈ reaches up to 502.8 K, indicating its broad applicability in high-temperature spintronic devices.