  In this work, employing spin-pumping techniques driven by both ferromagnetic
resonance (SP-FMR) and longitudinal spin Seebeck effect (LSSE) to manipulate
and direct observe orbital currents, we investigated the volume conversion of
spin-orbital currents into charge-current in YIG(100nm)/Pt(2nm)/NM2 structures,
where NM2 represents Ti or Ru. While the YIG/Ti bilayer displayed a negligible
SP-FMR signal, the YIG/Pt/Ti structure exhibited a significantly stronger
signal attributed to the orbital Hall effect of Ti. Substituting the Ti layer
with Ru revealed a similar phenomenon, wherein the effect is ascribed to the
combined action of both spin and orbital Hall effects. Furthermore, we measured
the SP-FMR signal in the YIG/Pt(2)/Ru(6)/Ti(6) and YIG/Pt(2)/Ti(6)/Ru(6)
heterostructures by just altering the stack order of Ti and Ru layers, where
the peak value of the spin pumping signal is larger for the first sample. To
verify the influence on the oxidation of Ti and Ru films, we studied a series
of thin films subjected to controlled and natural oxidation. As Cu and CuOx is
a system that is already known to be highly influenced by oxidation, this metal
was chosen to carry out this study. We investigated these samples using SP-FMR
in YIG/Pt(2)/CuOx(tCu) and X-ray absorption spectroscopy and concluded that
samples with natural oxidation of Cu exhibit more significant results than
those when the CuOx is obtained by reactive sputtering. In particular, samples
where the Cu layer is naturally oxidized exhibit a Cu2O-rich phase. Our
findings help to elucidate the mechanisms underlying the inverse orbital Hall
and inverse orbital Rashba-Edelstein-like effects. These insights indeed
contribute to the advancement of devices that rely on orbital-charge
conversion.
