Figure 4. MQT in spin filter S-F-S Josephson junctions.

(a) Thermal behaviour of the mean switching current I_mean (green up triangles, left axis) and of the s.d. σ (violet circles, right axis) in the absence of magnetic field. The red dashed line indicates the crossover temperature between macroscopic quantum tunnelling (MQT) regime (dark yellow background) and thermal activation (pink background). In the MQT regime both I_mean and σ saturate. (b) Comparison between thermal dependences of σ at 0 mT (violet circles) and at 1.1 mT (orange right triangles). In the presence of magnetic field, lower values of σ have been measured and T_cross is reduced, according to equation (1). T_cross has been determined by the intersection of the T^2/3 curve in the thermal activation regime (dashed green lines) and the mean value of σ in the MQT regime (black full lines). In (a) and in (b) the error bars have been determined by using the theory for propagation of statistical errors, from the equations defining the mean and the s.d. of the switching histograms.