Strong Anisotropic Order Parameters at All-Nitride Ferromagnet/Superconductor Interfaces

Proximity effects between superconductors and ferromagnets (SC/FM) hold paramount importance in comprehending the spin competition transpiring at their interfaces. This competition arises from the interplay between Cooper pairs and ferromagnetic exchange interactions. The proximity effects between transition metal nitrides (TMNs) are scarcely investigated due to the formidable challenges of fabricating high-quality SC/FM interfaces. We fabricated heterostructures comprising SC titanium nitride (TiN) and FM iron nitride (Fe₃N) with precise chemical compositions and atomically well-defined interfaces. The magnetoresistance of Fe₃N/TiN heterostructures shows a distinct magnetic anisotropy and strongly depends on the external perturbations. Moreover, the superconducting transition temperature T_C and critical field of TiN experience notable suppression when proximity to Fe₃N. We observe the intriguing competition of interfacial spin orientations near T_C (∼ 1.25 K). These findings not only add a new materials system for investigating the interplay between superconductor and ferromagnets, but also potentially provide a building block for future research endeavors and applications in the realms of superconducting spintronic devices.