Magnetism typically arises from the joint effect of Fermi statistics and repulsive Coulomb interactions, which favors ground states with non-zero electron spin. As a result, controlling spin magnetism with electric fields---a longstanding technological goal in spintronics and multiferroics---can be achieved only indirectly. Here, we experimentally demonstrate direct electric field control of magnetic states in an orbital Chern insulator, a magnetic system in which non-trivial band topology favors long range order of orbital angular momentum but the spins are thought to remain disordered. We use van der Waals heterostructures consisting of a graphene monolayer rotationally faulted with respect to a Bernal-stacked bilayer to realize narrow and topologically nontrivial valley-projected moiré minibands. At fillings of one and three electrons per moiré unit cell within these bands, we observe quantized anomalous Hall effects with transverse resistance approximately equal to h/2e2, which is indicative of spontaneous polarization of the system into a single-valley-projected band with a Chern number equal to two. At a filling of three electrons per moiré unit cell, we find that the sign of the quantum anomalous Hall effect can be reversed via field-effect control of the chemical potential; moreover, this transition is hysteretic, which we use to demonstrate nonvolatile electric field induced reversal of the magnetic state. A theoretical analysis indicates that the effect arises from the topological edge states, which drive a change in sign of the magnetization and thus a reversal in the favored magnetic state. Voltage control of magnetic states can be used to electrically pattern nonvolatile magnetic domain structures hosting chiral edge states, with applications ranging from reconfigurable microwave circuit elements to ultralow power magnetic memory.Work at UCSB was
primarily supported by the ARO under MURI W911NF-
16-1-0361. Measurements of twisted bilayer graphene
(Extended Data Fig. E8) and measurements at elevated
temperatures (Extended Data Fig. E3) were supported
by a SEED grant and made use of shared facilities of the
UCSB MRSEC (NSF DMR 1720256), a member of the
Materials Research Facilities Network (www.mrfn.org).
AFY acknowledges the support of the David and Lu-
cille Packard Foundation under award 2016-65145. AHM
and JZ were supported by the National Science Founda-
tion through the Center for Dynamics and Control of
8
Materials, an NSF MRSEC under Cooperative Agree-
ment No. DMR-1720595, and by the Welch Founda-
tion under grant TBF1473. CLT acknowledges support
from the Hertz Foundation and from the National Sci-
ence Foundation Graduate Research Fellowship Program
under grant 1650114. KW and TT acknowledge sup-
port from the Elemental Strategy Initiative conducted by
the MEXT, Japan, Grant Number JPMXP0112101001,
JSPS KAKENHI Grant Numbers JP20H00354 and the
CREST(JPMJCR15F3), JST.Center for Dynamics and Control of Material
