Analysis of the interface in ferromagnet insulator junctions by inelastic-electron-tunneling-spectroscopy

Inelastic-electron-tunneling-spectroscopy (IETS) has been applied to invest igate the electron states of the interface of Al/Al2O3/Co(d(Co) = 0 similar to 50 Angstrom)/Al and Al/Al2O3/Ni(d(Ni) = 0 similar to 50 Angstrom)/Al tu nneling junctions. A positive zero-bias anomaly was observed in the conduct ance curve of the junction with d(Co) less than or equal to 20 Angstrom. Co rrespondingly, the IET spectra showed a strong negative peak at 4 mV, while another broad peak was observed for the junctions with d(Co) greater than or equal to 10 Angstrom. These results were discussed in terms of the param agnetic impurity and magnon assisted tunneling processes. On the other hand , a positive peak was observed in the IET curves for the junction with Ni. The possibility of formation of an Ni-Al alloy was considered to explain th is result. (C) 1999 Elsevier Science B.V. All rights reserved.