Ferromagnetism and optical properties of SnS doped with two impurities: first-principles calculations.

Based on the first principles of the GGA method, the magnetic and optical properties of intrinsic SnS; Fe, Cr mono-doped SnS; and (Fe, Cr) co-doped SnS are studied. The results show that the ground states of Fe, Cr mono-doped SnS are spin polarized, and the magnetic moments caused are 1.99 μ and 3.00 μ, respectively. The magnetic moment of Fe mono-doped SnS is mainly produced by Fe:3d orbitals, and the magnetic moment of Cr mono-doped SnS is mainly produced by Cr:3d and Sn:4d orbitals. We calculate that in the (Fe, Cr) co-doped SnS system, Fe, Cr and the adjacent S atoms form a strong hybrid, that is, the closest S atom between Fe and Cr atoms mediates the spin polarization and ferromagnetic (FM) coupling. This promotes the formation of a Fe:3d-S:3p-Cr:3d coupling chain, so that (Fe, Cr) co-doped SnS obtains FM stability. In addition, with the introduction of Fe and Cr atoms, the absorption coefficient is the largest in the long-wavelength infrared region of 0.23-1.63 eV. This shows that Fe and Cr doping can make up for the lack of absorption of intrinsic materials in the infrared region. In summary, Fe, Cr doped SnS dilute magnetic semiconductors may be a good candidate in the field of spintronic devices.