DyOCl: A rare-earth based two-dimensional van der Waals material with strong magnetic anisotropy

Comparing with the widely known transitional metal based van der Waals (vdW) materials, rare-earth based ones are rarely explored in the research of intrinsic two-dimensional (2D) magnetism. In this work, we report the physical properties of DyOCl, a rare-earth based vdW magnetic insulator with a direct band gap of $\ensuremath{\sim}5.72\phantom{\rule{3.33333pt}{0ex}}\text{eV}$. The magnetic order of bulk DyOCl is determined by neutron scattering as the $A$-type antiferromagnetic structure below the N\'eel temperature ${T}_{N}=10\phantom{\rule{3.33333pt}{0ex}}\mathrm{K}$. The large magnetic moment near 10.1 ${\ensuremath{\mu}}_{B}$/Dy lies parallel to the $a$-axis with strong uniaxial magnetic anisotropy. At $2\phantom{\rule{3.33333pt}{0ex}}\text{K}$, a moderate magnetic field ($\ensuremath{\sim}2\phantom{\rule{3.33333pt}{0ex}}T$) applied along the easy axis generates spin-flip transitions and polarizes DyOCl to a ferromagnetic state. Density functional theory calculations reveal an extremely large magnetic anisotropy energy ($\ensuremath{-}5850\phantom{\rule{3.33333pt}{0ex}}\ensuremath{\mu}\text{eV}/Dy$) for DyOCl, indicating the great potential to realize magnetism in the 2D limit. Furthermore, the mechanical exfoliation of bulk DyOCl single crystals down to seven layers is demonstrated. Our findings suggest DyOCl is a promising material playground to investigate 2D $f$-electron magnetism and spintronic applications at the nanoscale.