Field and current-induced magnetization reversal studied through spatially resolved point-contacts

We present results from scanning tunneling microscopy based point-contact measurements of the local resistance in octagon shaped, Co(20 nm)/Cu (5 nm)/Fe(19)Ni(81)(2.5 nm) spin-valve rings. Through this technique one can detect the magnetoresistance with spatial resolution, and link it to magnetic domain wall motion within the ring. Measurements with varying currents indicate current-induced effects leading to offsets in the magnetic fields required for magnetic switching. The offsets can be attributed to current-induced spin-transfer torque effects for the thin Fe(19)Ni(81) layer and to Oersted field effects for the thick Co layer