  Magnetocaloric materials, which exploit reversible temperature changes
induced by magnetic field variations, are promising for advancing
energy-efficient cooling technologies. The potential integration of
two-dimensional materials into magnetocaloric systems represents an emerging
opportunity to enhance the magnetocaloric cooling efficiency. In this study, we
use atomistic spin dynamics simulations based on first-principles parameters to
systematically evaluate how magnetocaloric properties transition from
three-dimensional (3D) to two-dimensional (2D) ferromagnetic materials. We find
that 2D features such as reduced Curie temperature, sharper magnetic
transition, and higher magnetic susceptibility are beneficial for
magnetocaloric applications, while the relatively higher lattice heat capacity
in 2D can compromise achievable adiabatic temperature changes. We further
propose GdSi$_2$ as a promising 2D magnetocaloric material near hydrogen
liquefaction temperature. Our analysis offers valuable theoretical insights
into the magnetocaloric effect in 2D ferromagnets and demonstrates that 2D
ferromagnets hold promise for cooling and thermal management applications in
compact and miniaturized nanodevices.
