  We investigate transport properties of junctions between two spin-split
superconductors linked by a spin-polarized tunneling barrier. The
spin-splitting fields in the superconductors (S) are induced by adjacent
ferromagnetic insulating (FI) layers with arbitrary magnetization. The aim of
this study is twofold: On the one hand, we present a theoretical framework
based on the quasiclassical Green's functions to calculate the Josephson and
quasiparticle current through the junctions in terms of the different
parameters characterizing it. Our theory predicts qualitative new results for
the tunneling differential conductance, $dI/dV$, when the spin-splitting fields
of the two superconductors are non-collinear. We also discuss how junctions
based on FI/S can be used to realize anomalous Josephson junctions with a
constant geometric phase shift in the current-phase relation. As a result, they
may exhibit spontaneous triplet supercurrents in the absence of a phase
difference between the S electrodes. On the other hand, we show results of
planar tunneling spectroscopy of a EuS/Al/Al$_2$O$_3$/EuS/Al junction and use
our theoretical model to reproduce the obtained $dI/dV$ curves. Comparison
between theory and experiment reveals information about the intrinsic
parameters of the junction, such as the size of the superconducting order
parameter, spin-splitting fields and spin relaxation, and also about properties
of the two EuS films, as their morphology, domain structure, and magnetic
anisotropy.
