Intrinsic bitunable magnetism/polarity behavior in 2D Janus Cr 2 I 3 Y 3 (Y = F, Cl, or Br) systems

Two-dimensional (2D) magnetoelectric (ME) materials with spontaneous magnetism and polarity have drawn a lot of research interest due to their potentially valuable physics and spintronic applications. One of the obstacles in the current study of 2D ME materials is to achieve flexible magnetism/polarity switches because of a fundamental contradiction between magnetism and polarity. In this work, we propose an intrinsic magnetism/polarity switchable 2D Janus structure Cr 2 I 3 Y 3 (Y = F, Cl, or Br) with mechanical and thermodynamic stability. Janus Cr 2 I 3 Y 3 monolayers show indirect-gap semiconductors with ferromagnetic ordering. Intrinsic vertical electric polarity (EP) in Janus Cr 2 I 3 Y 3 structures is investigated by surface potential difference analysis and dipole calculations. We discover that there is an obvious ME coupling between magnetic anisotropy energy (MAE) and EP. MAE can be obviously tuned by rotating the orientations of spins within yz and zx vertical planes, and the easily distinguishable MAE on vertical planes has strong inherent relevance with vertical EP. Simultaneously, magnetic phase transition and magnetic moments can be manipulated by introducing vertical strain, which directly corresponds to the linear response of the EP strength. Our work provides a promising candidate for realizing the spintronic devices with multiple functionalities.