Long-distance spin current transmission in single-crystalline NiO thin films

Spin current transmission in antiferromagnets is one of the most interesting focuses in antiferromagnetic spintronics. Its study may provide access to spin superfluid physics, which gives rise to metastable spin supercurrents. In this work, we investigate the spin current transmission in a single-crystalline NiO (111) and NiO (001) of the NiO/Fe20Ni80 and Pt/NiO/Fe20Ni80 epitaxial films by the spin-pumping enhanced damping of FeNi. The spin transmission length is estimated to be λ_(NiO(111)) = 50 ± 4 nm and λ_(NiO(001))≫100 nm, for NiO (111) and NiO (001), respectively. The results are succinctly discussed in the framework of the spin superfluidity mechanism.