Supercurrent in ferromagnetic Josephson junctions with heavy-metal interlayers. II. Canted magnetization

Abstract

It has been suggested by theoretical works that equal-spin triplet pair correlations can be generated in Josephson junctions containing both a ferromagnet and a source of spin-orbit coupling. Our recent experimental work suggested that such triplet correlations were not generated by a Pt spin-orbit coupling layer when the ferromagnetic weak link had entirely in-plane anisotropy [Satchell and Birge, Phys. Rev. B 97, 214509 (2018)]. Here, we revisit the experiment using Pt again as a source for spin-orbit coupling and a [Co(0.4nm)/Ni(0.4nm)]×8/Co(0.4nm) ferromagnetic weak link with both in-plane and out-of-plane magnetization components (canted magnetization). The canted magnetization more closely matches theoretical predictions than our previous experimental work. Our results suggest that there is no supercurrent contribution in our junctions from equal-spin triplet pair correlations. In addition, this work includes systematic study of supercurrent dependence on Cu interlayer thickness, a common additional layer used to buffer the growth of the ferromagnet and which for Co may significantly improve the growth morphology. We report that the supercurrent in the [Co(0.4nm)/Ni(0.4nm)]×8/Co(0.4nm) ferromagnetic weak links can be enhanced by over two orders of magnitude by tuning the Cu interlayer thickness. This result has important application in superconducting spintronics, where large critical currents are desirable for devices.

Source-reported materials — not catalogue approval

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