Predicted intrinsic piezoelectric ferromagnetism in Janus monolayer MnSbBiTe4: a first principles study‡

Two-dimensional (2D) piezoelectric ferromagnetism (PFM) is essential for the development of the next-generation multifunctional spintronic technologies. Recently, the layered van der Waals (vdW) compound MnBi2Te4 as a platform to realize the quantum anomalous Hall effect (QAHE) has attracted great interest. In this work, the Janus monolayer MnSbBiTe4 with dynamic, mechanical and thermal stabilities is constructed from a synthesized non-piezoelectric MnBi2Te4 monolayer by replacing the top Bi atomic layer with Sb atoms. The calculated results show that monolayer MnSbBiTe4 is an intrinsic ferromagnetic (FM) semiconductor with a gap value of 0.25 eV, whose easy magnetization axis is out-of-plane direction with magnetic anisotropy energy (MAE) of 158 μeV per Mn. The predicted Curie temperature TC is about 20.3 K, which is close to that of monolayer MnBi2Te4. The calculated results show that the in-plane d11 is about 5.56 pm V−1, which is higher than or comparable to those of other 2D known materials. Moreover, it is found that strain engineering can effectively tune the piezoelectric properties of Janus monolayer MnSbBiTe4. The calculated results show that tensile strain can improve the d11, which is improved to be 21.16 pm V−1 at only 1.04 strain. It is proved that the ferromagnetic order, semiconducting properties, out-of-plane easy axis and a large d11 are robust against electronic correlations. Our work provides a possible way to achieve PFM with a large d11 in well-explored vdW compound MnBi2Te4, which makes it possible to use the piezoelectric effect to tune the quantum transport process.