Tunnel magnetoresistance and spin torque switching in MgO-based magnetic tunnel junctions with a Co/Ni multilayer electrode

We have fabricated MgO-barrier magnetic tunnel junctions with a Co/Ni switching layer to reduce the demagnetizing field via interface anisotropy. With a fcc-(111) oriented Co/Ni multilayer combined with an FeCoB insertion layer, the demagnetizing field is 2 kOe and the tunnel magnetoresistance can be as high as 106%. Room-temperature measurements of spin-torque switching are in good agreement with predictions for a reduced critical current associated with the small demagnetization for antiparallel-to-parallel switching. For parallel-to-antiparallel switching the small demagnetization field causes spatially nonuniform reversal nucleated at the sample ends, with a low energy barrier but a higher switching current.