S1-S5

The values of $\alpha$ are larger than the reported value of single layer of CFMS ($\sim$ 0.004) \[24\]. This enhancement in the values of $\alpha$ is the indication of the spin pumping. However, we cannot rule out other effects e.g. MPE, and any impurities which may contribute in enhancing the value of $\alpha$ (see Eq. (\[q6\])). In order to investigate the MPE or magnetic dead layer formation at the interface, we measured saturation magnetization (*$M_s$*) for all the samples by SQUID magnetometer (data not shown). The measured values of *$M_s$* for all the samples are found to be 861 emu/cc (S1), 842 emu/cc (S2), 792 emu/cc (S3), 845 emu/cc (S4) and 807 emu/cc (S5). The change in the values of Ms with the thickness of Pt may be due to MPE or dead layer formation \[31,32\].

Inverse spin Hall effect measurement {#inverse-spin-hall-effect-measurement .unnumbered}
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In order to confirm the spin pumping in our system, we performed ISHE measurements on all the samples as shown in schematic Fig. \[fig1\](d). The measurements are carried out at 11 mW power and 7 GHz frequency.

![Voltage (*$V_{meas}$*) measured across the sample with applied magnetic field along with FMR signal for sample S1 at 