  Two-dimensional magnets are promising for nanoscale spintronic applications.
Currently, most available candidates are based on $3d$ transition metal
compounds, with hexagonal or honeycomb lattice geometry. Here, a GdCl$_3$
monolayer with $4f$ moments is theoretically studied, which can be exfoliated
from its existing bulk. Its orthorhombic structure and hendecahedral ion cages
are unique in two-dimensional. Furthermore, a significant structural
reconstruction is caused by the implantation of Li atoms into its interstitial
position, which also lead to ferromagnetism via a double-exchange-like process.
Its highly anisotropic conductance may be peculiarly useful for
nanoelectronics.
