Colossal Triplet Spin-Valve Effect in Heterostructures containing 100\% Spin Polarised Fe0.8Co0.2Si

At the interface between a superconductor (S) and ferromagnet (F), an inhomogeneity can convert singlet Cooper pairs into the (spin aligned) long ranged triplet component (LRTC). Manipulation of the LRTC forms the basis of the emerging field of super-spintronics. The prototypical device in this field is the superconducting spin valve (SSV), where LRTC generation can be controlled by the relative orientation of two F layers in a heterostructure. This generation is accompanied by an observed suppression in the superconductors critical temperature (T$_{c}$). Motivated by a recent report of ‘colossal proximity effects’ in a F$_{1}$/F$_{2}$/S SSV containing 100\% spin polarized CrO$_{2}$ as the bottom drainage layer\footnote{A. Singh, \textit{et al.}, \textbf{Phy. Rev. X} 5, 021019}, we explore the possibility of using highly spin polarized, Fe$_{0.8}$Co$_{0.2}$Si as F$_{1}$. The observed T$_{c}$ suppression of 830 mK is nearly an order of magnitude larger than previous studies using standard F layers with Nb, and is consistent with that seen in CrO$_{2}$. Our results confirm the special importance of high spin polarization in the formation of the LRTC, and we offer the field a new material as a fundamental building block for incorporation into future super-spintronic devices.