Zusammenfassung
We report on the temperature dependence of the spatially modulated spin-polarization amplitude $\ensuremath\DeltaK_spin$, which is a hallmark of the superconducting Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state. For that, we use $^13C$ nuclear magnetic resonance (NMR) spectroscopy performed on the organic conductor $\beta^''\ensuremath-(ET)_2SF_5CH_2CF_2SO_3$. From a comparison of our experimental results to a comprehensive modeling of the $^13C$ NMR spectra, we determine the evolution of $\ensuremath\DeltaK_spin$ upon condensation of the FFLO state. Further, the modeling of the spectra in the superconducting phase allows to quantify the decrease of the average spin susceptibility, stemming from the spin-singlet coupling of the superconducting electron pairs in the FFLO state of $\beta^''\ensuremath-(ET)_2SF_5CH_2CF_2SO_3$.
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