Biaxial strain tuned magnetic anisotropy of ferromagnetic penta-MnN2 monolayer

Ferromagnetic (FM) materials with high Curie temperature, large spin polarization ratio and large perpendicular magnetic anisotropic (PMA) are the basis of constructing practical spintronic devices. Using first-principles calculations, electronic property, magnetism and magnetic anisotropic energy (MAE) of penta-MnN2 monolayer are investigated. The calculated results indicate that penta-MnN2 monolayer is FM half-metal and exhibits PMA. The PMA is induced by Mn atom of 0.207 meV/Mn, which is one or two orders of magnitude larger than those of bulk Co (−65 μeV/atom), Fe (−1.4 μeV/atom) and Ni (2.7 μeV/atom). It is worth noting that the structure, magnetism and MAE of penta-MnN2 monolayer can be manipulated by applying biaxial strain. By applying tensile strain of 3%, penta-MnN2 monolayer has a second energy minimum and remains the original crystalline symmetry, but the N–N bond length has a sudden change. The MAE of Mn atom in penta-MnN2 monolayer can be enhanced by 21% with compressive strain compared to the unstrained systems. Meanwhile, the MAE decreases with the increase of tensile strain, and it exhibits a more significant decrease due to the sudden drop of N–N bond with tensile strain. These results may broaden the development of two-dimensional (2D) FM materials, which have potential applications in 2D spintronic nanodevices.