Crypto-superconductivity in RuSr2GdCu2O8

The susceptibility chi = chi' + i chi " of RuSr2 GdCu2O8 powders at 2 K has been deduced from sc and de magnetizations with their particle size d from 800 to 10 mum and grain size 1-5 mum. It is observed that the loss part, c hi ", scales with d over a field range of 0.0001 to 100 Oe, suggesting that the supercurrent is homogeneously distributed over particles as small as 1 0 mum. However, the inductance part, chi', decreases with d systematically and drastically. An effective penetration depth as large as 30-50 mum is ne eded, which suggests a very small super-carrier concentration. Crypto-super conductivity is proposed to accommodate the data.