TUNNEL-JUNCTIONS ON 1 2/4-Y-BA-CU-O SINGLE-CRYSTALS/

We have studied the 1:2:4 phase of the Y-Ba-Cu-O compound by means of tunneling spectroscopy on single crystal based junctions. The crystals , with T-c approximate to 80 K, have been chemically etched before the deposition of the counterelectrode in form of a thin film through a m etallic mask. We have compared the tunneling spectra to those obtained on the Y123 system. The features at +/-20 mV of the 1:2:3 phase are s till observed in the 1:2:4 phase, while the low bias features at +/-5 mV are not present in the tunneling characteristics of the Y124 compou nd. The experimental results are discussed in terms of the different C uO chain role in the Y123 and Y124 systems.