Antiferromagnetic Spintronics

Antiferromagnetic 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 antiferromagnetic spintronics. One approach involves 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 non-collinear antiferromagnetic Γ5g and Γ4g phases. We have predicted that by stoichiometry engineering ANMn3 can be tuned close to the critical transition point between the Γ5g and Γ4g phases, at which the Néel vector switching can be achieved by strain or spin-transfer torque. Combining density functional theory calculations and atomistic spin-dynamics modeling based on the Landau-Lifshitz Gilbert-Slonczewski equation, we have   demonstrated that the spin torque can efficiently control the noncollinear antiferromagnetic order in antiperovskite materials. The switching can be detected though the anomalous Hall effect being zero or finite for the Γ5g and Γ4g phases, respectively, due to symmetry of the Berry curvature.

Another approach comprises the subfield of antiferromagnetic spintronics known as topological antiferromagnetic spintronics, where the Néel vector is used to electrically manipulate the symmetry related topological states. Based on density-functional theory calculations, we have demonstrated that room temperature antiferromagnetic 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 have predicted that the nonlinear anomalous Hall effect can be used to detect the Néel vector in most compensated antiferromagnets supporting the antidamping spin-orbit torque. We showed 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. As a specific example, we considered half-Heusler alloy CuMnSb, whose Néel vector can be switched by the antidamping spin-orbit torque. Based on density functional theory calculations, we showed that the nonlinear anomalous Hall effect in CuMnSb results in a measurable Hall voltage under conventional experimental conditions.

References
  1. 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).
  2. 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).
  3. 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).
  4. 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.
  5. 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).
  6. 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).

Controlling a Dirac point or a Dirac nodal line by the Néel vector in MnPd2.

Different non-collinear magnetic phases in AFM antiperovskite GaNMn3: (a) Γ5g, (b) Γ4g, and (c) M-1. 

Spin dynamics in antiperovskite NiNMn3.