Pt and CoB trilayer Josephson [Formula: see text] junctions with perpendicular magnetic anisotropy.

We report on the electrical transport properties of Nb based Josephson junctions with Pt/Co $$_{68}$$ B $$_{32}$$ /Pt ferromagnetic barriers. The barriers exhibit perpendicular magnetic anisotropy, which has the main advantage for potential applications over magnetisation in-plane systems of not affecting the Fraunhofer response of the junction. In addition, we report that there is no magnetic dead layer at the Pt/Co $$_{68}$$ B $$_{32}$$ interfaces, allowing us to study barriers with ultra-thin Co $$_{68}$$ B $$_{32}$$ . In the junctions, we observe that the magnitude of the critical current oscillates with increasing thickness of the Co $$_{68}$$ B $$_{32}$$ strong ferromagnetic alloy layer. The oscillations are attributed to the ground state phase difference across the junctions being modified from zero to $$\pi $$ . The multiple oscillations in the thickness range $$0.2~\leqslant ~d_\text {CoB}~\leqslant ~1.4$$  nm suggests that we have access to the first zero- $$\pi $$ and $$\pi $$ -zero phase transitions. Our results fuel the development of low-temperature memory devices based on ferromagnetic Josephson junctions.