Generation of pure spin circular current in an open magnetic quantum ring with vanishing net magnetization

We report the existence of a nondecaying circular spin current in an antiferromagnetic (AFM) quantum ring with zero net magnetization. In the presence of a finite voltage bias, a net circular spin current is generated in the ring geometry without accompanying any charge current. Such a bias-driven pure spin circular current in a magnetic ring with vanishing net magnetization has not been reported so far to the best of our knowledge. Employing a tight-binding framework to describe the nanojunction which is formed by connecting the AFM ring with two electrodes, we compute spin-dependent transport quantities along with spin circular current using the standard Green's function formalism. Most of the results are analyzed for the AFM ring where neighboring magnetic moments are arranged in antiparallel directions and different other configurations of magnetic moments are also taken into account for comparison. Various aspects are critically discussed like ring-electrode interface sensitivity, impurities at different lattice sites, ring-electrode coupling strength, spin-dependent scattering factor, Fermi energy, and system size, to make the present communication a self-contained one. For some input conditions, a nonzero circular charge current may appear but that is too small compared to the spin circular current. All the results are valid for a wide range of physical parameters which proves the robustness of the phenomenon of bias-driven circular spin current in an AFM nanoring. In the end, we also provide experimental perspectives for designing AFM ring systems. Our analysis red paves the way for obtaining a pure spin current in open quantum systems, offering opportunities to explore various simple and complex AFM loop substructures in the presence of external baths.