Josephson Junctions with a CoGd Compensated Ferrimagnet Barrier

We have studied the rare earth-transition metal ferrimagnet Co_1-xGd_x as the barrier in ferromagnetic Josephson junctions. At a particular thickness, the Co and Gd moments cancel leading to a zero-moment compensation point [1]. Due to differing participation of Co and Gd, the transport current is spin-polarized even at the compensation point [2]. This suggests that CoGd could be used for applications in spintronics and superconducting electronics requiring low magnetic moment but spin-polarized current. One potential application is in the development of a π Josephson junction with low moment and stray field. We present SQUID VSM data characterizing the compensation point in thin films at cryogenic temperatures. We also show transport data over a range of CoGd thicknesses that indicate the presence of a 0 - π transition at 1.2 nm.

 

[1] Hansen et al., J.  App. Phys. 66, 756 (1989);

[2] Naylor et al., Phys. Rev. B 85, 064410 (2012)