Layer-dependent piezoelectricity and robust magnetic anisotropy in Janus CrSCl

Abstract

Two-dimensional Janus materials with both piezoelectricity and ferromagnetism hold great potential for multifunctional spintronic devices. Using first-principles calculations, we investigate monolayer and few-layer CrSCl, a Janus-type van der Waals material with out-of-plane asymmetry, to explore its layer-dependent electronic, piezoelectric, and magnetic properties. We find that stacking-induced dipoles increase the electrostatic potential difference between surfaces, saturating beyond four layers. The potential gradient induces layer-resolved band shifts, leading to a reduced bandgap and a semiconductor-to-semimetal transition. Enhanced screening and depolarization effects suppress the strain-induced polarization change, causing the out-of-plane piezoelectric coefficient d31 to decrease overall with increasing thickness. In contrast, the magnetic anisotropy remains stable: despite the emergence of additional layer-derived states approaching the Fermi level, both the out-of-plane easy axis and magnetic anisotropy energy remain unchanged. These results highlight few-layer CrSCl as a versatile platform for engineering coexisting piezoelectric and magnetic functionalities, with layer-dependent piezoelectricity and robust magnetic anisotropy.