Evidence for triplet superconductivity in Josephson junctions with barriers of the ferromagnetic Heusler alloy Cu2 MnAl

Abstract

We have studied Josephson junctions with barriers prepared from the Heusler compound Cu2 MnAl. In the as-prepared state the Cu2 MnAl layers are nonferromagnetic and the critical Josephson current density jc decreases exponentially with the thickness of the Heusler layers dF. On annealing the junctions at 240°C the Heusler layers develop ferromagnetic order and we observe a dependence jc (dF) with jc strongly enhanced and weakly thickness dependent in the thickness range 7.0< dF <10.6nm. We interpret this feature as an indication of a triplet component in the superconducting pairing function generated by the specific magnetization profile inside thin Cu2 MnAl layers. © 2010 The American Physical Society.