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arXiv · 0712.1322

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

P. SanGiorgio·S. Reymond·M. R. Beasley·J. H. Kwon·K. Char
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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 $\pmΔ_0$, whereas intermediate-thickness samples have an anomalous ``double-peak'' structure. For thicker samples ($d_F \geq 3.5$ 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 $\pmΔ_0$ 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.

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P. SanGiorgio, S. Reymond, M. R. Beasley, J. H. Kwon, K. Char. 2007-12-09. Anomalous double peak structure in Nb/Ni superconductor/ferromagnet tunneling DOS. https://doi.org/10.1103/physrevlett.100.237002

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