Regulation of transition temperature and magnetic anisotropy in 2D multiferroic monolayer through electron donating and withdrawing groups adsorption

The discovery of two-dimensional (2D) magnetic materials ushers in the engineering of future magnetoelectric nanodevices and spintronics, however, it is limited by the lack of a material platform with simultaneously large magnetic anisotropy and high transition temperature. Using a recently synthesized CrSe₂monolayer as a demonstration, the impact on magnetism and electronics is studied via first-principles calculations by functionalizing the monolayer with electron-donating and electron-withdrawing groups namely NH₂and NO₂. The magnetic ground state of the CrSe₂changes from the stripe antiferromagnetic to the ferromagnetic state after functionalization. The transition temperature of CrSe₂-NO₂and CrSe₂-NH₂enhances to 105 and 70 K, respectively, due to the expansion of the CrSe₂superlattice. Besides, the magnetic anisotropy energy (MAE) of the CrSe₂-NO₂increases to 1.12 meV/Cr along the in-plane direction due to the electron-withdrawing effect of the NO₂group. Oppositely, the electron-donating effect will decrease the MAE. Moreover, robust out-of-plane electric polarization is induced into the functionalized CrSe₂monolayer, relying on the semiconducting nature and asymmetric geometry along the<i>z</i>direction. These findings demonstrate the critical role of functional groups in regulating the magnetic and electronic properties of 2D multiferroic structures, providing a general approach for controllable 2D spintronic applications.