Bulk and Interface Effects Based on Rashba-Like States in Ti and Ru Nanoscale-Thick Films: Implications for Orbital-Charge Conversion in Spintronic Devices

Abstract

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.

20pages, 7 figures

References in corpus (7)

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• Giant Orbital Hall Effect in Transition Metals: Origin of Large Spin and Anomalous Hall Effects
• Orbitronics: Orbital Currents in Solids
• Giant orbital Hall effect and orbital-to-spin conversion in 3d, 5d, and 4f metallic heterostructures
• Orbital Rashba effect in surface oxidized Cu film
• Microscopic Theory of Rashba Interaction in Magnetic Metal
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Cited by in corpus (6)

• Orbital Pumping in Ferrimagnetic Insulators
• Anomalous Spin and Orbital Hall Phenomena in Antiferromagnetic Systems
• Negative orbital Hall effect in Germanium
• Probing orbital currents through inverse orbital Hall and Rashba effects
• Anisotropy-Driven Anomalous Inverse Orbital Hall Effect in Fe Films
• Investigating spin and orbital effects via spin-torque ferromagnetic resonance