Revealing Interfacial Orbital Transport in Nonmagnet/Ferromagnet Bilayers by the Absence of Orbital Hall Magnetoresistance

Orbital angular momentum transport has emerged as a promising route for spin-orbitronic devices, yet its transport behavior remains under debate and is often assumed to follow the phenomenology of spin transport. Here, we reveal the distinct nature of interfacial orbital transport through the absence of orbital Hall magnetoresistance (OMR) in nonmagnet/ferromagnet bilayers, challenging the general assumption that orbital transport mimics spin transport. Despite the observation of giant orbital torques, which confirms the injection of orbital currents, thickness-dependent magnetoresistance measurements reveal that the magnetoresistance signal is dominated by the intrinsic magnetoresistance of the ferromagnet and current shunting, with no discernible OMR contribution. We attribute this contradiction to magnetization-independent orbital absorption within the ferromagnet, which allows the generation of orbital torque as one relaxation pathway but suppresses the interfacial reflection required for OMR. Additionally, we find that texture-induced magnetoresistance, self-torque, and interfacial effects in Ni-based bilayers may obscure genuine orbital signals, suggesting that caution is required when employing Ni in orbitronic studies. These findings clarify the distinct physical rules governing orbital transport and provide a simple method to distinguish between spin and orbital currents.