Electron transport through antiferromagnetic spin textures and skyrmions in a magnetic tunnel junction

Abstract

An ideal layered $\hat{x}$-polarized antiferromagnet (AFM) between two antialigned $\pm \hat{z}$ polarized ferromagnetic (FM) contacts transmits no current due to a $\pi$ phase difference of the matrix elements coupling the spin degenerate states to the two FM contacts. The ratio of the two matrix elements coupling the two spin degenerate $\hat{x}$ AFM states to a $\hat{z}$ FM contact is determined by the exchange energy and the eigenstate energy. Inserting a normal metal layer or tunnel barrier layer between one FM contact and the AFM alters this phase difference, and, due to the unequal weighting of the two spins at the interface, it also breaks the spin degeneracy of the two AFM states. The broken symmetry of the matrix elements combined with the broken degeneracy of the AFM states, result in a Fano resonance in the transmission and a turn-on of the $T_{\uparrow ,\downarrow }$ transmission channel. Such a magnetic tunnel junction geometry with two antialigned $\pm \hat{z}$ FM contacts can electrically detect an AFM skyrmion. The AFM skyrmion serves as an analogue of the oblique polarizer in the triple polarizer experiment. Resistances and resistance ratios are calculated and compared for FM and AFM skyrmions in a magnetic tunnel junction.

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