  Spin-singlet Cooper pairs consisting of two electrons with opposite spins
cannot directly penetrate from a superconductor to a half-metal (fully spin
polarized ferromagnets) which blocks the superconducting proximity effect
between these materials. In this paper we demonstrate that, nevertheless, two
half-metallic layers electrically coupled to the superconducting film
substantially affect its critical temperature and produce the spin valve
effect. Within the tight-binding model for the atomically thin multilayered
spin valves we show that depending on the details of the electron energy
spectra in half-metals the critical temperature as a function of the angle
between the spin quantization axes in half-metals can be either monotonically
increasing or decreasing. This finding highlights the crucial role of the band
structure details in the proximity effect with half-metals which cannot be
adequately treated in the quasiclassical theories.
