  In the quantum Hall regime of graphene, antiferromagnetic and spin-polarized
ferromagnetic states at the zeroth Landau level compete, leading to a canted
antiferromagnetic state depending on the direction and magnitude of an applied
magnetic field. Here, we investigate this transition at 2.7 K in graphene Hall
bars that are proximity coupled to the ferrimagnetic insulator
Y$_{3}$Fe$_{5}$O$_{12}$. From nonlocal transport measurements, we demonstrate
an induced magnetic exchange field in graphene, which lowers the magnetic field
required to modulate the magnetic state in graphene. These results show that a
magnetic proximity effect in graphene is an important ingredient for the
development of two-dimensional materials in which it is desirable for ordered
states of matter to be tunable with relatively small applied magnetic fields (>
6 T).
