Analysis of carrier spin polarisation using the Spin Hall Effect

摘要

Production and analysis of carrier spin polarisation in a subject material (2), by applying an electric field (4) to the subject material (2) causing an electrical current to flow across the material (2), thereby inducing carrier polarisation within the material (2) in a direction (6, 8) perpendicular to the direction of current flow, carriers of one spin orientation concentrating at a first edge (12) of the subject material (2) and carriers of the opposite orientation concentrating at a second edge (10) of the material (2), opposite to the first edge (12) under the action of the Spin Hall Effect (SHE); allowing spin polarised carriers to tunnel into a ferromagnetic material from the subject material (2) in at least a portion adjacent one of the first or second edges (12, 10) of the subject material (2); and measuring the tunnelling magnetoresistance (TMR) between the ferromagnetic material and the subject material (2) at the first or second edge (12, 10). The subject material is preferably a semiconductor, preferably an aluminium gallium arsenide, Al0.4Ga0.6As. Tunnelling to the ferromagnetic material may be enabled by applying a magnetic field to the ferromagnetic material to induce carrier spin polarisation therein. Measurement of the tunnelling magnetoresistance between a portion of an edge (12, 10) of the subject material (2) and the ferromagnetic material, for a known carrier spin in the ferromagnetic material, provides an indication of spin polarisation in the subject material (2). The particular advantage of the present invention is that it enables direct analysis of the Spin Hall Effect properties of the subject material (2) (rather than indirect analysis, e.g. by optical means).