Orbital-to-charge conversion via orbital pumping in Nb-based bilayers

The orbital pumping, serving as the orbital counterpart to spin pumping in the angular momentum transport, provides a robust and versatile mechanism for orbital current generation. However, the research on orbital pumping remains in its nascent stage, with fundamental mechanisms and practical applications yet to be fully explored. In this work, we demonstrate efficient injection of orbital currents from a ferromagnetic layer into an adjacent niobium layer in ferromagnet/niobium (FM/Nb; FM = Co, Fe19Ni81) bilayers via orbital pumping. The injected orbital currents in the niobium layer are converted into detectable charge currents through the inverse orbital Hall effect. We quantitatively evaluated the orbital pumping magnitudes in both systems and determined the orbital diffusion lengths of Nb across distinct structures. This result not only deepens the understanding of orbital pumping and orbital current dynamics across diverse material systems but also provides critical insights for advancing the emerging field of orbitronics.