Antiferromagnetic Spintronics

Antiferromagnetic (AFM) spintronics is an emerging field of research, which exploits the Néel vector to control spin- and orbital-dependent transport properties. Due to being robust against magnetic perturbations, producing no stray fields, and exhibiting ultrafast dynamics, antiferromagnets can serve as promising functional materials for spintronic applications, which may expand to very diverse areas ranging from terahertz information technologies to artificial neural networks.

We are exploring new approaches and new material platforms, which can be exploited in AFM spintronics. One approach involves AFM tunnel junctions where the relative orientaion of the Néel vectors of the two AFM metals controls resistance of the junction resulting in a tunneling magnetoresistance (TMR) effect.  Using RuO₂ as a representative antiferromagnet exhibiting a non-spin-degenerate Fermi surface, we design a RuO₂/TiO₂/RuO₂ (001)  AFM tunnel junction and predict the TMR effect as large as ~500%. 

In another approch, we consider the Néel vector switching in non-collinear antiferromagnets ANMn₃ (A = Ga, Ni, Zn, etc.) with an antiperovskite crystal structure. These compounds are characterized by the competing AFM Γ_5g and Γ_4g phases.  Combining density functional theory calculations and atomistic spin-dynamics modeling, we demonstrate that the spin torque can efficiently control the noncollinear AFM order in the antiperovskite materials. The switching can be detected though the anomalous Hall effect being zero or finite for the Γ_5g and Γ_4g phases, respectively, due to symmetry of the Berry curvature.

Further, we explore a posibility to use the Néel vector to electrically manipulate topological states. We demonstrate that room temperature AFM metal MnPd₂ allows the electrical control of the Dirac nodal line by the Néel spin-orbit torque. The reorientation of the Néel vector leads to switching between the symmetry-protected degenerate state and the gapped state associated with the dispersive Dirac nodal line at the Fermi energy.

Finally, we predict that a nonlinear anomalous Hall effect can be used to detect the Néel vector in most compensated antiferromagnets supporting the antidamping spin-orbit torque. We show that the magnetic crystal group symmetry of these antiferromagnets combined with spin-orbit coupling produce a sizable Berry curvature dipole and hence the nonlinear anomalous Hall effect. We demonstrate this behaviour for half-Heusler alloy CuMnSb, whose Néel vector can be switched by the antidamping spin-orbit torque.

References

1. D.-F. Shao, S.-H. Zhang, M. Li, C.-B. Eom, and E. Y. Tsymbal, “Spin-neutral currents for spintronics,” Nature Communications 12, 7061 (2021).
2. G. Gurung, D.-F. Shao, and E. Y. Tsymbal, “Transport spin polarization of noncollinear antiferromagnetic antiperovskites,” Physical Review Materials 5, 124411  (2021).
3. T. Nan, C. X. Quintela, J. Irwin, G. Gurung, D. F. Shao, J. Gibbons, N. Campbell, K. Song, S. Y. Choi, L. Guo, R. D. Johnson, P. Manuel, R. V. Chopdekar, I. Hallsteinsen, T. Tybell, P. J. Ryan, J. W. Kim, Y. S. Choi, P. Radaelli, D. Ralph, E. Y. Tsymbal, M. S. Rzchowski, and C. B. Eom, “Controlling spin current polarization through non-collinear antiferromagnetism,” Nature Communications 11, 4671 (2020).
4. G. Gurung, D.-F. Shao, and E. Y. Tsymbal, “Spin-torque switching of non-collinear antiferromagnetic antiperovskites,” Physical Review B – Rapid Communications 101, 140405(R) (2020).
5. D.-F. Shao, S.-H. Zhang, G. Gurung, W. Yang, and E. Y. Tsymbal, “Nonlinear anomalous Hall effect for Néel vector detection,” Physical Review Letters 124, 067203 (2020).
6. H. Takenaka, S. Sandhoefner, A. A. Kovalev, and E. Y. Tsymbal, “Magnetoelectric control of topological phases in graphene,” Physical Review B 100, 125156 (2019); Editor’s Suggestion.
7. Gautam Gurung, Ding-Fu Shao, Tula R. Paudel, and Evgeny Y. Tsymbal, "Anomalous Hall conductivity of noncollinear magnetic antiperovskites," Physical Review Materials 3, 044409 (2019).
8. D.-F. Shao, G. Gurung, S.-H. Zhang, and E. Y. Tsymbal, “Dirac nodal line metal for topological antiferromagnetic spintronics,” Physical Review Letters 122, 077203 (2019).