Phase-Transition-Induced Ferroelectric and Magnetic Switching in Two-Dimensional CuMnP2Se6 under Ultra-Low Electric Fields

Abstract Low-field electric control of magnetic phase transitions is critical for the development of energy-efficient spintronic and non-volatile memory technologies. Yet, the weak magnetoelectric coupling in most known two-dimensional multiferroics hinders their practical implementation. Here, using crystal structure prediction and high-throughput first-principles calculations, we identify four previously unexplored bimetallic thio(seleno)phosphate multiferroics, XMnP₂(S/Se)₆ (X = Cu, Au), all exhibiting robust in-plane spontaneous polarization—contrasting with the predominantly out-of-plane behavior in this material family—which effectively mitigates depolarization effects. In particular, CuMnP₂Se₆ hosts two stable C2-symmetric ferroelectric phases with opposite in-plane polarizations and distinct magnetic orders. Remarkably, an electric field as small as 0.001 V/Å can simultaneously reverse the polarization and induce an antiferromagnetic-to-ferromagnetic transition. The associated barrier is exceptionally low (51 meV/f.u.), yielding a sizable magnetoelectric coefficient of 0.04 Gcm/V. These results highlight a viable strategy for realizing electric-field-driven magnetism in intrinsic two-dimensional multiferroics under experimentally feasible conditions.