Kondo-Fano resonance in atomic-scale contacts for ferromagnetic metals

The electrical conductance of cobalt (Co) nano-scale contacts prepared by a Mechanically Controllable Break Junction (MCBJ) technique has been studied to understand the origin of Fano resonance in ferromagnetic atomic-sized contacts. In an atomic-scale contacts, the zero-bias anomaly is well-fitted by the Fano formula. The characteristic temperature, which is introduced as the fitting parameter of that formula, exhibits the log-normal distribution. These indicate that the anomaly is likely caused by Kondo effect. Moreover, the zero-bias anomaly is observed in large scale contacts where the bulk ferromagnetic properties should be retained. This suggests the coexistence of Kondo effect and ferromagnetism.