Optical observation of the orbital Hall effect in a light metal Ti, Mn, and Cu

Orbitronics aims for control of the orbital current in non-magnetic materials. Among various techniques to measure orbital, the optical method employing the magneto-optical Kerr effect has the advantages of high sensitivity and vector-and-time resolution. I will present the magneto-optical observation of the orbital Hall effect in a light metal Ti. The Kerr rotation by the orbital magnetic moment accumulated at Ti surfaces due to the orbital Hall current is measured, whose result agrees with theoretical calculations quantitatively and is supported by the orbital torque measurement in Ti-based magnetic heterostructures. In addition, I will present the optical detection of the orbital Hall effect in other light metals of Mn and Cu. The direct detection of orbital accumulation on the surfaces of light metals provides important information for orbital generation, transport, and relaxation.