Evidence for triplet superconductivity in Josephson junctions with barriers of the ferromagnetic Heusler alloy Cu2MnAl

We have studied Josephson junctions with barriers prepared from the Heusler compound Cu2MnAl. In the as-prepared state the Cu2MnAl layers are nonferromagnetic 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 degrees 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 < d(F) < 10.6 nm. We interpret this feature as an indication of a triplet component in the superconducting pairing function generated by the specific magnetization profile inside thin Cu2MnAl layers.