Fig. 2: Coexistence of ferro- and antiferromagnetism in Fe3GeTe2(FGT)/CrBr3 barriers.
From: Moiré magnetism in CrBr3 multilayers emerging from differential strain
Schematic structure (a) optical micrographs (b) and an example of current-voltage (I-V) characteristics (c) of a FGT/CrBr3/graphene (Gr) tunnel barrier device (data measured at T = 2 K). d, e for positive and negative bias, electrons injected from the FGT or the Gr electrode respectively, tunnel through the CrBr3 barrier (~8.5 nm), with transport occurring in the Fowler-Nordheim (FN) regime. f Tunneling magnetoconductance δG(H, 2 K) for electrons injected from the FGT contact (top panel; V = 2.1 V; the blue and red curves are the magnetoconductance \({\delta G}_{\uparrow }\) and \({\delta G}_{\downarrow }\) measured when sweeping the magnetic field in the direction indicated by the arrows). The hysteresis is a manifestation of the spin-valve effect, resulting in a larger (smaller) conductance when the magnetizations of FGT and CrBr3 are parallel (antiparallel) to each other. The spin-valve magnetoconductance (\({\delta G}_{\uparrow }\) -\(\,{\delta G}_{\downarrow }\), middle panel) is superimposed on a sizable magnetoconductance background (\({\delta G}_{{{\rm{bg}}}}\) = ((\({\delta G}_{\uparrow }\) + \({\delta G}_{\downarrow }\))+(\(\left|{\delta G}_{\uparrow }\,-\,{\delta G}_{\downarrow }\right|\)))/2, bottom panel) that resembles the magnetoconductance measured in AFM CrBr3 barriers (compare to b). g Tunneling magnetoconductance measured with electrons injected from the graphene electrode (top panel; V = −2.1 V). The spin valve effect (middle panel) is absent but the background magnetoconductance (bottom panel) is virtually identical to that measured when injecting electrons from the FGT contact. The observation of spin-valve effect and of the magnetoconductance background in a same device provide direct evidence for the coexistence of FM of AFM regions in the CrBr3 barrier. The same behavior has been observed in all tunnel barriers that we realized with FGT contacts (in all measurements, the magnetic field is applied perpendicular to the layers).
