  Superconductor/ferromagnet/superconductor heterostructures exhibit a
so-called long-range proximity effect provided some layers of conical magnet
Holmium are included in the respective interface regions. The Ho layers lead to
a spin-flip process at the interface generating equal-spin spin-triplet pairing
correlations in the ferromagnet. These equal-spin spin-triplet pairing
correlations penetrate much further into the heterostructure compared to the
spin-singlet and unequal-spin spin-triplet correlations which occur in the
absence of Ho. Here we present calculations of this effect based on the
spin-dependent microscopic Bogoliubov-de Gennes equations solved within a
tight-binding model in the clean limit. The influence of the ferromagnet and
conical magnet layer thickness on the induced equal-spin spin-triplet pairing
correlations is obtained and compared to available experimental data. It is
shown that, in agreement with experiment, a critical minimum thickness of
conical magnet layers has to be present in order to observe a sizeable amount
of equal-spin spin-triplet pairing correlations.
