Zigzag edges of graphene are predicted to host magnetic electronic states, critical for spintronics, but an experimental confirmation of these magnetic conduction channels remains elusive. Here we report the signatures of magnetism in zigzag graphene nanoribbons (zGNRs) embedded in hexagonal boron nitride. Hexagonal boron nitride provides crucial edge stabilization, enabling the direct probing of this intrinsic magnetism. Scanning nitrogen-vacancy-centre microscopy initially confirmed magnetism in zGNR. Subsequently, an ~9-nm-wide zGNR transistor was fabricated with a sub-50-nm channel length. Magnetotransport measurements at 4 K revealed distinct Fabry–Pérot-like interference patterns, indicating coherent transport. A large, anisotropic magnetoresistance (~175 Ω, ~1.3%) was observed, persisting well above room temperature. These findings strongly corroborate the existence of robust magnetic ordering in the zGNR edge state. This hexagonal-boron-nitride-embedded zGNR system offers an effective platform for future graphene-based spintronic devices.

Zigzag graphene nanoribbons (zGNRs) are known as quasi one-dimensional strips of graphene associated by parallel zigzag edges. These localized zigzag edges are predicted to possess a unique magnetic state near the Fermi level that can be promising for spintronic device applications. Recent progresses in the synthesis of graphene nanoribbons (GNRs) enabled the fabrication of atomically precise GNRs, allowing the electrical manipulation and detection of edge states. Symmetry-protected topological phases zero-mode metallicity and spin-polarized edge statesare subsequently revealed via advanced scanning probe spectroscopy in GNRs. However, a direct experimental probing of magnetism by electrical methods in zigzag edge structures still remains elusive. Limited by surface diffusivity and kinetic factors on catalytic substrates, GNRs made from bottom-up assembly have length typically in the range of tens of nanometres, which is too short to be technologically practical for reliable device fabrication. Moreover, the open edges of zGNRs are of relatively high chemical reactivity and can, thus, cause instability or inhomogeneous doping in electronic properties. Finally, the edge states in narrow zGNRs could become antiferromagnetically coupled so strongly that it becomes difficult to detect a sizable electrical signal under a moderate magnetic field. All the above reasons create hurdles in the direct transport measurement on magnetism in GNR electronic devices. The successful fabrication of oriented zGNRs embedded in hexagonal boron nitride (hBN) could potentially overcome the aforementioned difficulties and enable the exploration of spin transport in the ultimate limit of miniaturization. The zigzag-oriented hBN trenches were produced by zinc nanoparticle cutting. Subsequently, the zigzag-oriented hBN trenches were filled with zGNR by gaseous catalysed chemical vapour deposition. These zGNRs are now stabilized by in-plane graphene–boron nitride bonding, having a carbon–boron interface at one edge and a carbon–nitrogen interface at the opposite edge. Thus, narrow zGNRs were predicted to exhibit an insulating antiferromagnetic state with negligible contribution to the electrical signal, similar to hydrogen-terminated zGNRs. On another aspect, the asymmetric structure of the zGNR–BN interface could, in turn, weaken the superexchange interaction between the two inequivalent carbon edge states; therefore, now only a moderate magnetic field is required to manipulate the magnetic order of the zGNR. More interestingly, it was further predicted that the edges of zGNRs could become a half-metal once an in-plane homogeneous electric field is applied across the width direction. Unfortunately, the transverse-electric field required is experimentally too high (normally higher than 1 V nm−1) to realize half-semimetallicity in ultranarrow zGNRs. However, in a slightly wider zGNR, the superexchange interaction between edge states could become very weak. In addition, a built-in electric field is naturally created by the difference in electrostatic potentials at the carbon–boron and carbon–nitrogen interfaces, which could promote the formation of half-semimetallicity in zGNRs’ edge states. As such, the zGNRs embedded in hBN provide a unique material platform to detect the intrinsic edge-state magnetism by transport measurements in a proper magnetic field, which could largely deepen the understanding of zGNR’s magnetic properties.