Fig. 2: Schematics of different types of tunnel junctions and TMR effects.

a Schematics of a conventional MTJ where two ferromagnetic (FM) electrodes are separated by a tunnel barrier. b Mechanism of TMR in a conventional MTJ. Conduction (indicated by block arrows) between left and right FM electrodes for parallel (P) and antiparallel (AP) magnetization (indicated by large arrows). Red and blue circles denote the Fermi surfaces of the ferromagnet for up-spin (small red arrows) and down-spin (small blue arrows) electrons. Angle θ refers to the spin orientation with respect to the magnetization in the left electrode. c Schematics of an AFMTJ with collinear exchange-split AFM electrodes (C-AFMTJ). d Mechanism of TMR in C-AFMTJ. Conduction between left and right AFM electrodes for P and AP Néel vectors (indicated by double-arrows). Red and blue ellipses denote the Fermi surfaces of the antiferromagnet for up- and down-spin electrons. Angle θ refers to the spin orientation with respect to the Néel vector in the left electrode. e Schematics of an AFMTJ with non-collinear AFM electrodes (NC-AFMTJ). f Mechanism of ETMR. The NC-AFM electrodes have fully spin-polarized conduction channels within the area indicated by crossing ellipses with the spin polarization vector having different orientation θ (indicated by varying color). Electrons in these channels can efficiently tunnel through a tunnel barrier due to its low-decay-rate evanescent states supporting transmission. Matching (mismatching) of the 100% polarized conduction channels in the two electrodes for the P (AP) state produces ETMR.