Robust spin transfer torque in antiferromagnetic tunnel junctions

We theoretically study the current-induced spin torque in antiferromagnetic tunnel junctions, composed of two semi-infinite antiferromagnetic layers separated by a tunnel barrier, in both clean and disordered regimes. We find that the torque enabling the electrical manipulation of the N'eel antiferromagnetic order parameter is out of plane $\sim \mathbf{n}\times \mathbf{p}$, while the torque competing with the antiferromagnetic exchange is in-plane $\sim \mathbf{n}\times (\mathbf{p}\times \mathbf{n})$. Here, $\mathbf{p}$ and $\mathbf{n}$ are the N'eel order parameter direction of the reference and free layers, respectively. Their bias dependence shows similar behavior as in ferromagnetic tunnel junctions, the in-plane torque being mostly linear in bias while the out-of-plane torque is quadratic. Most importantly, we find that the spin transfer torque in antiferromagnetic tunnel junctions is much more robust against disorder than in antiferromagnetic metallic spin-valves due to the tunneling nature of spin transport.