Spin-oribit torques in Mn2Au/HM bilayers

Abstract

Antiferromagnets are promising materials for spintronic applications due to their unique features such as ultrafast spin dynamics and robustness against external magnetic fields. An efficient way to manipulate the antiferromagnetic (AFM) order is to use spin-orbit torque (SOT), which utilizes the conversion of electric current to spin through the spin-orbit interaction. Current-induced switching of the AFM order has been demonstrated experimentally in several antiferromagnets including Mn2Au. It has a broken sublattice inversion symmetry, which gives rise to opposite spin polarization on each sublattice under an electrical current. The staggered spin polarization results in a non-staggered field-like (FL) SOT, which is suitable for the switching of the AFM order. It is also possible to utilize the damping-like SOT originated from a spin current generated by a heavy metal (HM) layer adjacent to Mn2Au. Here by using first-principles calculations, we calculate the SOTs of a Mn2Au/HM bilayer, where HM is W or Pt. By expanding the SOT using vector spherical harmonics, layer-resolved angular dependence of SOT is obtained. For FL SOT, it has a large contribution from the Mn2Au and a small contribution from the HM. For DL SOT, it has most of the contribution from the HM. FL SOT is non-staggered on each sublattice and it dominates the behavior of spin dynamics. DL SOT is staggered on each sublattice so that its net effect on spin dynamics is negligible.