Superconducting intermediate state of white tin studied by muon-spin-rotation spectroscopy

The local magnetic field in the bulk of superconducting single crystal b tin was measured near and across the transition between the normal ~N! and intermediate~I! state atT50.08 K. With varying applied fieldHa , the data indicate a reversible phase transition within the I state atHt'295 Oe, interpreted as a transition from the laminar to a tubular structure. Near the I→N transition, occurring at HcI50.98Hc05300 Oe, the fieldB in theN domains is strongly inhomogeneous with B̄,Hc0, it grows with the decrease of Ha towards the value Hc05305.560.5 Oe. On loweringHa in theN state, a large ‘‘field supercooling’’ ( dH/Hc'6%) of this state was observed.