​Magnetoresistance (MR) refers to the phenomenon where the electrical resistance of a material varies based on its magnetic configuration. Traditional MR effects, such as anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR), and tunneling magnetoresistance (TMR), primarily originates from s-d exchange interactions. While, spin Hall magnetoresistance (SMR) and unidirectional spin Hall magnetoresistance (USMR) have also been observed, even in insulating systems, arising from spin-dependent scattering mechanisms. These effects have been significant in understanding the fundamental properties of magnetic systems and have further applications in technologies like magnetic sensing and data storage.

Recent studies have highlighted the significance of orbital angular momentum (OAM) in magnetoresistance phenomena, particularly within ferromagnetic bilayer systems. Exploring the role of OAM transport opens new avenues in spin-orbitronic applications. For instance, the observation of unidirectional orbital magnetoresistance (UMR) in light-metal/ferromagnet bilayers indicates that OAM can influence magnetoresistance without relying on strong spin-orbit coupling materials. Additionally, the emergence of orbital related magnetoresistance emphasizes the potential of harnessing OAM for advanced spintronic functionalities. ​

To this end, we focus on investigating the role of OAM in magnetoresistance phenomena within ferromagnetic bilayer systems. By employing angular-dependent electric transport measurements, we aim to study orbital Hall magnetoresistance (OHR) and orbital Rashba-Edelstein magnetoresistance (OREMR) in systems lacking strong spin-orbit coupling. Through thickness and temperature-dependent characterizations, we can elucidate the diffusion mechanisms and OAM transport's influence on magnetization dynamics. Moreover, examining novel magnetoresistance effects arising from orbital-dependent electron scattering, magnon scattering, and orbital-to-spin conversion will provide deeper insights into orbital-to-spin conversion processes. These findings are crucial for optimizing spin-orbitronic devices based on light metals and orbital transport mechanisms.