  As a recent successfully exfoliated non van der Waals layered material,
AgCrS2 has received a lot of attentions. Motivated by its structure related
magnetic and ferroelectric behavior, a theoretical study on its exfoliated
monolayer AgCr2S4 has been carried out in the present work. Based on density
functional theory, the ground state and magnetic order of monolayer AgCr2S4
have been determined. The centrosymmetry emerges upon two-dimensional
confinement and thus eliminates the bulk polarity. Moreover, two-dimensional
ferromagnetism appears in the CrS2 layer of AgCr2S4 and can persist up to room
temperature. The surface adsorption has also been taken into consideration,
which shows a nonmonotonic effect on the ionic conductivity through ion
displacement of the interlayer Ag, but has little impact on the layered
magnetic structure.
