Current flux imaging of a micromagnetic electrofoil

Spin current—the flow of angular momentum mediated by electrons—is a unique probe of non-trivial phases in ultrathin magnetic heterostructures. Electron spin, however, is highly sensitive to nearby electromagnetic fields; thus, it is important to characterize nonlocal effects in spintronic devices. The high spin orbit coupling of platinum in conjunction with the ferrimagnetic insulator Yttrium Iron Garnet (YIG) provides an optimal platform for evaluating spin current as a robust probe. Combining scanning photovoltage microscopy with a highly uniform rotating magnetic field, we probe the photoresponse of atomically pristine Pt/YIG heterostructures. Similar to how tracers in a wind tunnel map the flow of air around an aerodynamic airfoil, we use a scanning laser beam as a source of directional spin and charge current to map the flow around precisely engineered wing shaped devices, or electrofoils. Spin current scatters electrons in plane and away from the external magnetic field, producing moving charges that interact with the local electric flux to generate a global voltage. By manipulating the spin current we produce unique images, which exhibit surprising geometric effects, that are fully described by a straightforward application of the Shockley-Ramo theorem.