Magnetic penetration depth of single-crystalline SmFeAsO1-xFy

We report measurements of the in-plane magnetic penetration depth lambda in single crystals of SmFeAsO1-xFy (x similar or equal to y similar or equal to 0.2) with T-c similar or equal to 44 K. We find that at low temperature lambda has an exponential temperature dependence which suggests that the Fermi surface is fully gapped. The magnitude of the minimum energy gap, Delta(1)=1.1 +/- 0.1k(B)T(c) at T=0, is significantly smaller than the BCS weak-coupling value suggesting that the gap is either strongly anisotropic or varies significantly between the different Fermi-surface sheets. Our data are well fitted by a two-gap model with the larger gap (Delta(2)=1.7 +/- 0.2k(B)T(c)) associated with similar to 80% of the total superfluid density.