Half-metallicity and Curie temperature enhancement of CrI3 through boron atoms adsorption

Abstract

Monolayer chromium iodide (CrI 3 ) as a two-dimensional material with intrinsic ferromagnetism has been successfully prepared experimentally, expanding the applications of two-dimensional materials in the field of spintronics . In this paper, we have investigated the effect of boron atoms adsorption on the electronic structure, magnetic properties of monolayer CrI 3 through first-principles calculation based on density functional theory . Our results show that each boron atom adsorption enhance the magnetic moment of CrI 3 by 0.25 μ B . When the adsorption concentration increases from 1B@CrI 3 to 2B@CrI 3 , a semiconductor to half-metallicity transition occurs; when the concentration increases up to 4B@CrI 3 , CrI 3 tunes to semiconductor. The Monte Carlo simulation based on the Ising model predicts the Curie temperature are 81.5 K, 117.7 K, 129.4 K and 143.9 K for 1B@CrI 3 , 2B@CrI 3 , 3B@CrI 3 and 4B@CrI 3 , much higher than that of pristine CrI 3 . Our calculation results are theoretically instructive for the application of CrI 3 in spintronic devices. • The electronic structures and magnetic properties of boron adsorption CrI 3 have been investigated. • The semiconductor-half metallicity-semiconductor transition of adsorption systems depended on boron concentration. • The Curie temperature of CrI 3 can be largely enhanced through boron atoms adsorption. Firstly, we calculated the band structure of the 2 × 2 × 1 supercell CrI 3 (shown in Fig. 1(c)), and the results show that the monolayer CrI 3 is an indirect bandgap semiconductor with a bandgap of 1.16 eV. The intrinsic magnetic moment is 24 μ B for CrI 3 supercell, it means that the magnetic moment is 6 μ B for CrI 3 unit cell. The magnetic moments mainly come from the contribution of Cr atoms, and the magnetic moment of each Cr atom is 3 μ B , which is consistent with the results of previous studies [26,35]. The properties of CrI 3 with different concentrations of boron atoms adsorption are shown in Table 1, each adsorbed B atom increases the magnetic moment average to each CrI 3 primitive cell by about 0.25 μ B . This indicates that the magnetic properties of CrI 3 can be effectively tuned by boron atoms adsorption. The Bader charge analysis shows that each B atom transfers about 0.13 electrons to CrI 3 . The magnetic moments of top position Cr ( M ІCr ) do not much change, while the magnetic moments for other Cr atoms ( M ⅡCr ) increased with adsorption concentration. Since the B atoms are adsorbed on the surface of the CrI 3 layer, the nearly equal electrons per B atom transfer from the B atoms to CrI 3 increased almost equal magnetic moment of Cr atoms, which may be the reason for the increased total magnetic moments of 0.25 μ B of the monolayer CrI 3 .