Self‐Intercalation Tunable Interlayer Exchange Coupling in a Synthetic van der Waals Antiferromagnet

One of the most promising avenues in 2D materials research is the synthesis of antiferromagnets employing 2D van der Waals (vdW) magnets. However, it has proven challenging, due in part to the complicated fabrication process and undesired adsorbates as well as the significantly deteriorated ferromagnetism at atomic layers. Here, the engineering of the antiferromagnetic (AFM) interlayer exchange coupling between atomically thin yet ferromagnetic CrTe2 layers in an ultra‐high vacuum‐free 2D magnetic crystal, Cr5Te8 is reported. By self‐introducing interstitial Cr atoms in the vdW gaps, the emergent AFM ordering and the resultant giant magnetoresistance effect are induced. A large negative magnetoresistance (10%) with a plateau‐like feature is revealed, which is consistent with the AFM interlayer coupling between the adjacent CrTe2 main layers in a temperature window of 30 K below the Néel temperature. Notably, the AFM state has a relatively weak interlayer exchange coupling, allowing a switching between the interlayer AFM and ferromagnetic states at moderate magnetic fields. This work represents a new route to engineering low‐power devices that underpin the emerging spintronic technologies, and an ideal laboratory to study 2D magnetism. A giant magnetoresistance is induced by self‐introducing interstitial Cr atoms in the van der Waals gaps of CrTe2 layers. A large negative magnetoresistance (10%) with a plateau‐like feature is revealed, resulting from the antiferromagnetic interlayer coupling between the adjacent CrTe2 layers below the Néel temperature. These findings offer a new horizon in engineering functional structures for 2D magnet‐based spintronics.