Experimental exploration of magnetism in ultrathin M$_{\mathrm{2}}$P$_{\mathrm{2}}$X$_{\mathrm{6}}$ flakes

Transition metal phosphorus chalcogenides M$_{\mathrm{2}}$P$_{\mathrm{2}}$X$_{\mathrm{6}}$ (M $=$ Mn, Ni, Fe, etc.; X $=$ S, Se, Te, etc.) constitute a large family of van der Waals materials that possess rich magnetic phases. We systematically studied the magnetic behaviors of ultrathin M$_{\mathrm{2}}$P$_{\mathrm{2}}$X$_{\mathrm{6}}$ flakes. We found that magnetism in thin layers is suppressed, revealing a strong dimensionality effect. Our work unveils the dominant physics that controls the magnetic behavior in vdW layers, which can guide the design of magnetic vdW layers, heterostructures, and superlattics.