Investigations on the Magnetic Properties of Thick Films of BKBO

Abstract

Single crystalline thick films of the superconductor Ba 1Àx K x BiO y with wide range of composition x were studied. We first prepared the superconducting films with potassium content x = 0.55 to 0.67. The systematic exploration of the thick films with T c % 30± ±31 K and J c (5 K) % 5 Â 10 5 Acm ± ±2 (x = 0.36 and 0.38) reveals that for 4.2 to 20 K the field dependences J c (B) are well described by the collective pinning theory. The investigation of the pinning force density F p (B) shows an unusual scaling behaviour for thick film with x = 0.38.

Magnetization relaxation, critical current density, and vortex dynamics in aBa0.66K0.32BiO3+δsingle crystal

“…9 we show the F p normalized to its maximum value as a function of reduced field b = H/H irr , and H irr is the irreversible magnetic field determined using a criterion of J s = 20 A/cm 2 . Although there is uncertainty to determine H irr , the curves of normalized pinning force at different temperatures seem to scale well and have the similar maximum value, which is different from the poor scaling results observed in the thick films of BKBO 58 . The maximum of the pinning force density locates at b ≈ 0.47.…”