Inelastic magnon and phonon excitations in Al1-xCox/Al1-xCox-oxide/Al tunnel junctions

Magnetoelectric properties of the tunnel junctions, Al(50 nm)/Al2O3(1.2 nm) /Al(50 nm) (x=0), Al(55 nm)/Al2O3(1.0 nm)/Co(55 nm) (x=0 and top electrode is Co), and Al1-xCox(55 nm)/Al1-xCox-oxide(d nm)/Al(55 nm) (x=0.25, 0.50, 0 .75, and 1.0), were investigated. Oxides of Al1-xCox (x=0, 0.25, 0.50, 0.75 , and 1.0) were chosen as barrier materials in order to modulate the magnon and phonon excitations in the barrier layer and the interfaces. It was sho wn that the magnon and phonon excitations were the main sources of inelasti c scattering in the tunneling processes for the conduction electrons in the se tunnel junctions at nonzero bias voltages. The magnon effects were enhan ced in the Co-rich barrier junctions. The Al-O-Co phonon energy decreased w ith increasing Co composition between the Al-O and Co-O phonon energies bas ed on an Al-O-Co stretching mode in the Al1-xCox-oxide barrier as vibration al frequency of crystal lattice decreased with increasing Co composition. ( C) 2001 American Institute of Physics.