Fig. 1: Tunneling conductance of CrBr₃ multilayers.

a Schematics of the crystal structure of CrBr₃: the orange balls represent the Cr atoms with the associated spins pointing perpendicularly to the layers; the light blue balls represent the Br atoms. b Temperature dependence of the magnetization measured on bulk CrBr₃ crystals with a magnetic field of 1 mT applied perpendicular to the layers. The inset shows the plot of dM/dT, with a sharp minimum close to 32 K, corresponding to the Curie temperature of CrBr₃. c Tunneling current as a function of applied voltage measured on a 7 (blue curve) and 8 (orange curve) layer CrBr₃ device at T = 2 K (curves of the same color in panels d and e represent data measured on the same devices). The up left inset is a cartoon representation of our hBN-encapsulated graphene/CrBr₃/graphene tunnel junction devices. The down right inset shows that -for sufficiently large applied bias V- \({{{{{{\mathrm{log}}}}}}}\,(I/{V}^{2})\) is linearly proportional to 1/V, as expected in the Fowler–Nordheim tunneling regime. To avoid Joule heating problems, we used relatively small bias voltage (as discussed in ref. ¹⁵; V = 1 V and V = 1.4 V for the 7 and 8 layer devices, respectively) to measure the temperature and magnetic field dependence of the conductance shown in this and later figures, represented by the stars in the inset. d Magnetoconductance δG(H, T) ≡ [G(H, T) − G(0, T)]/G(0, T) measured at T = 2 K on the 7 and 8 layer devices. The magnetic field is applied perpendicular to the CrBr₃ ab-plane. e Temperature dependence of the zero-field tunneling conductance of the 7 and 8 layer devices, exhibiting an increase of approximately 300%, as T is lowered from T_c to 2 K.