  A superconductor with a spin-split excitation spectrum behaves as an ideal
ferromagnetic spin-injector in a tunneling junction. It was theoretical
predicted that the combination of two such spin-split superconductors with
independently tunable magnetizations, may be used as an ideal $absolute$
spin-valve. Here we report on the first switchable superconducting spin-valve
based on two EuS/Al bilayers coupled through an aluminum oxide tunnel barrier.
The spin-valve shows a relative resistance change between the parallel and
antiparallel configuration of the EuS layers up to 900% that demonstrates a
highly spin-polarized currents through the junction. Our device may be pivotal
for realization of thermoelectric radiation detectors, logical element for a
memory cell in cryogenics superconductor-based computers and superconducting
spintronics in general.
