Fano profiles in palladium nanoconstrictions

We have performed the differential conductance (dI/dV) measurements of palladium (Pd) nanoconstrictions made by a mechanically controllable break junction technique to examine the origin of Fano resonance observed in atomic sized contacts of ferromagnetic metals such as Ni. As a quasimagnetic metal of Pd undergoing ferromagnetic transition by downsizing, the dI/dV spectra exhibit zero-bias anomalies with a dip, peak or asymmetric shape and are well-fitted by the Fano formula. Moreover, the amplitude of the anomalies varies with the temperature in logarithmic scale, suggesting that the origin of the anomaly is caused by the Kondo effect. These results indicate that the appearance of Kondo effect would be ubiquitous in ferromagnetic atomic scale contacts.