  The capacity to externally manipulate magnetic properties is highly desired
from both fundamental and technological perspectives, particularly in the
development of magnetoelectronics and spintronics devices. Here, using
first-principles calculations, we have demonstrated the ability of controlling
the magnetism of magnetized graphene monolayers by interfacing them with a
two-dimensional ferroelectric material. When the 3$d$ transition metal (TM) is
adsorbed on the graphene monolayer, its magnetization easy axis can be flipped
from in-plane to out-of-plane by the ferroelectric polarization reversal of
In$_2$Se$_3$, and the magnetocrystalline anisotropy energy (MAE) can be high to
-0.692 meV/atom when adopting the Fe atom at bridge site with downward
polarization. This may be a universal method since the 3$d$ TM-adsorbed
graphene has a very small MAE, which can be easily manipulated by the
ferroelectric polarization. As a result, the inherent mechanism is analyzed by
second variation method.
