Evidence for triplet superconductivity in Josephson junctions with ferromagnetic Cu${}_2$MnAl-Heusler barriers

Abstract

We have studied Josephson junctions with barriers prepared from the Heusler compound Cu${}_2$MnAl. In the as-prepared state the Cu${}_2$MnAl layers are non ferromagnetic and the critical Josephson current density $j_c$ decreases exponentially with the thickness of the Heusler layers $d_F$. On annealing the junctions at 240\degree C the Heusler layers develop ferromagnetic order and we observe a dependence $j_c(d_F$) with $j_c$ strongly enhanced and weakly thickness dependent in the thickness range 7.0 nm < $d_F$ < 10.6 nm. We attribute this feature to a triplet component in the superconducting pairing function generated by the specific magnetization profile inside thin Cu${}_2$MnAl layers.

4 pages, 4 figures