  Polycrystalline samples and single crystals of SmFeAs1-xPxO1-y were
synthesized and grown employing different synthesis methods and annealing
conditions. Depending on the phosphorus and oxygen content, the samples are
either magnetic or superconducting. In the fully oxygenated compounds the main
impact of phosphorus substitution is to suppress the N\'eel temperature TN of
the spin density wave (SDW) state, and to strongly reduce the local magnetic
field in the SDW state, as deduced from muon spin rotation measurements. On the
other hand the superconducting state is observed in the oxygen deficient
samples only after heat treatment under high pressure. Oxygen deficiency as a
result of synthesis at high pressure brings the Sm-O layer closer to the
superconducting As/P-Fe-As/P block and provides additional electron transfer.
Interestingly, the structural modifications in response to this variation of
the electron count are significantly different when phosphorus is partly
substituting arsenic. Point contact spectra are well described with two
superconducting gaps. Magnetic and resistance measurements on single crystals
indicate an in-plane magnetic penetration depth of 200 nm and an anisotropy of
the upper critical field slope of 4-5. PACS number(s): 74.70.Xa, 74.62.Bf,
74.25.-q, 81.20.-n
