Abstract

The magnetic-field dependence of the in-plane magnetic penetration depth λab for optimally doped SmFeAsO1−xFy was investigated by combining torque magnetometry, SQUID magnetometry, and muon-spin rotation. The results obtained from these techniques show all a pronounced decrease of the superfluid density ρs∝λab− 2 as the field is increased to 1.4 T. This behaviour of ρs is analysed within a two-band model with self-consistently derived coupled gaps and ρs=ρs1+ρs2, where ρs1 related to the larger gap is field independent, and ρs2 related to the smaller gap is strongly suppressed with increasing field.