Lower critical fields in BKBO single crystals

Abstract

We performed dc-magnetization measurements in low magnetic fields on single crystals of Ba1-xKxBiOy with the different potassium content. The single crystal reveal the superconducting transition at 29-31K. It is shown that the lower critical fields HCl in crystals amount to 104 Oe, 126 and 112 Oe. The values of the penetration depth (lambda) are equal to 2530 A, 2430 A and 2670 A for x equals 0.34, 0.37 and 0.4 respectively.