Anomalous double peak structure in Nb/Ni superconductor/ferromagnet tunneling DOS

Abstract

We have experimentally investigated the density of states (DOS) in Nb/Ni (S/F) bilayers as a function of Ni thickness, $d_F$. Our thinnest samples show the usual DOS peak at $\pm {\Delta }_0$, whereas intermediate-thickness samples have an anomalous ``double-peak'' structure. For thicker samples ($d_F\ge 3.5$ nm), we see an ``inverted'' DOS which has previously only been reported in superconductor/weak-ferromagnet structures. We analyze the data using the self-consistent non-linear Usadel equation and find that we are able to quantitatively fit the features at $\pm {\Delta }_0$ if we include a large amount of spin-orbit scattering in the model. Interestingly, we are unable to reproduce the sub-gap structure through the addition of any parameter(s). Therefore, the observed anomalous sub-gap structure represents new physics beyond that contained in the present Usadel theory.

4 pages, 3 figures

References in corpus (3)

• A spin triplet supercurrent through the half-metallic ferromagnet CrO2
• Spectroscopy and critical temperature of diffusive superconducting/ferromagnetic hybrid structures with spin-active interfaces
• Density of states in SF bilayers with arbitrary strength of magnetic scattering

Cited by in corpus (4)

• Theory of superconducting and magnetic proximity effect in S$\mid$F structures with inhomogeneous magnetization textures and spin-active interfaces
• Odd triplet superconductivity in superconductor-ferromagnet structures with a narrow domain wall
• Proximity effect in ferromagnet/superconductor hybrids: from diffusive to ballistic motion
• Superconducting/ferromagnetic diffusive bilayer with a spin-active interface: a numerical study