Effect of lead resistance on spin-dependent tunneling junction with ion-beam deposited AlN barrier

Directly ion-beam deposited AlN films were used as insulating barriers for spin-dependent tunneling junctions, and the effect of the lead resistance o n the measured Delta R/R was investigated. 'Bow-tie' junctions with AlN thi cker than 15 Angstrom showed non-linear I-V characteristics with Delta R/R of 1.4%. Junctions with AlN films thinner than 12 Angstrom showed small 'ne gative' resistance with Delta R/R of - 14%. The finite-element analysis was used to simulate the current flow and the measured resistance of the 'bow- tie' structure with different resistance ratios of the tunneling junction t o the lead. The result of simulation shows when the ratio is smaller than 0 .077, the measured resistance becomes negative, and Delta R/R is significan tly enhanced by the lead effect. (C) 1999 Elsevier Science B.V. All rights reserved.