Ballistic electron emission microscopy on spin valve structures

Spin valve structures, as employed in base layers of spin valve transistor devices, are characterized by ballistic electron emission microscopy (BEEM). In detail, Co-Cu-Permalloy-Au layers sputtered onto n-type GaAs bulk substrates were studied. BEEM spectra taken on these multilayers show that magnetocurrents on the order of 600% can be achieved even at room temperature. Small area images (400 nm x 400 nm) show that the spin filtering effect of the spin valves is quite homogeneous on the submicron scale. On larger scales, magnetic domains were imaged close to the switching field of the spin valve structure.