Composite Spin Hall Conductivity from Non-collinear Antiferromagnetic Order in PtMn3

Abstract

Thin film antiferromagnets have emerged as strong candidates for state-of-the-art spintronic applications, promising efficient spin current generation that is critical for the development of low power non-volatile electronics. Intrinsic spin current generation in thin films has been primarily studied in systems with interfacial symmetry breaking, surface spin current from a topological insulator state, or a bulk spin Hall effect in heavy metal systems such as W, Ta, or Pt. In general, the high symmetry of these nonmagnetic systems limits the spin Hall conductivity tensor components to that of a left-handed polarization texture around the applied current direction, with out-of-plane spin currents having only y polarization. In contrast, the reduced symmetry of non-collinear antiferromagnets allows for additional linear-response-driven spin conductivities, including longitudinal and out-of-plane spin currents with x,z polarization, though the measured effects so far have been small and non-tunable. Understanding the intrinsic origin of these out-of-plane spin currents with atypical polarization could enable new developments in low power non-volatile spin-based electronics.

In this work, multi-component out-of-plane spin Hall conductivities are discovered in L12 ordered antiferromagnetic PtMn3 thin films that are uniquely generated in the non-collinear state. The maximum spin torque efficiencies (Js/Je ~ 0.3) are found to be significantly larger than in Pt (~ 0.1), a canonical spin Hall effect material. Additionally, the spin Hall conductivities in the non-collinear state exhibit an orientation-dependent anisotropy, which can be used to select for a dominant component. The work presented here demonstrates symmetry control through the magnetic lattice as a pathway to tailored functionality in magnetoelectronic systems.