Orbital Hall Magnetoresistance in Cr/CoFeB Structures

Spin-orbitronics devices based on spin Hall effect is a strong candidate for new generation memory devices. To realize this device the bilayer structure composed of a ferromagnet and a heavy metal layer should show sizable spin-orbit torque to manipulate magnetization of the devices. In this study, we investigate orbital transport in Cr-based heterostructures, because Cr has sizable orbital Hall angle and good conductivity. We found that orbital Hall magnetoresistance shows strong Cr-thickness dependence with the obtained diffusion length similar to 3 nm. Through a comparative experiment with the Cr/Pt/CoFeB structure in which the Pt layer was inserted, the orbital-spin conversion phenomenon by spin-orbit coupling can be understood. This study provides important information about orbital-related transport phenomenon in the Cr layer.