Two-dimensional [CaCl]+·e− with its strippable feasibility as an applicable electride with room-temperature ferromagnetism and extremely low work function

Abstract

Electrides in a two-dimensional (2D) scale, especially those that capture inherent magnetism and have low work functions, have shown great application prospects in nanoscale spintronic devices and electronic emitters. However, searching for ideal 2D magnetic electrides is still a great challenge. Herein, based on first-principles calculations, we demonstrate that 2D CaCl is strippable from the heterostructure of experimental CaCl/graphene and reveal that the freestanding 2D CaCl has a novel electride phase. In this material, sufficient electrons are trapped in the lattice voids and act as anions within the positive crystalline framework, following the electride form of [CaCl]⁺·e⁻. Due to the unique electron behaviour of electrides, the 2D [CaCl]⁺·e⁻ possesses a series of interesting physical phenomena: (1) the electride [CaCl]⁺·e⁻ exhibits room-temperature ferromagnetism, where the magnetic moment originates from the excess electrons with an s-like orbital feature rather than the atomic orbital ones, which is drastically different from traditional 2D ferromagnets; (2) the electride [CaCl]⁺·e⁻ shows magnetic metal characteristics, and by doping with halogen elements, its electronic structure can be effectively regulated; (3) most remarkably, the FM electride [CaCl]⁺·e⁻ shows an extremely low work function (2.65 eV). This value is the lowest among the electrides in 2D materials reported so far. Besides, the dimension of excess electrons can be effectively regulated by controlling the temperature. This work provides an excellent candidate to investigate 2D magnetic electrides and their associated applications.